v3.26.1
Shareholder Report, Holdings (Details)
Apr. 30, 2026
C000092936 [Member] | Xcel Energy Inc 6 25 10 15 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092936 [Member] | American AgCredit Corp 5 25 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092936 [Member] | BNP Paribas S A 8 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092936 [Member] | NextEra Energy Capital Holdings Inc Series U 6 50 06 01 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092936 [Member] | Hartford Insurance Group The Inc 6 04 02 12 47 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092936 [Member] | Land O Lakes Inc 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000092936 [Member] | Credit Agricole S A 7 13 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.50%
C000092936 [Member] | Barclays PLC 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.90%
C000092936 [Member] | Wells Fargo And Co Series L 7 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.10%
C000092936 [Member] | Bank of America Corp 6 63 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.60%
C000092936 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 15.40%
C000092936 [Member] | Industrial Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000092936 [Member] | Consumer Staples Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.50%
C000092936 [Member] | Consumer Discretionary Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092936 [Member] | Communications Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.50%
C000092936 [Member] | Real Estate Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092936 [Member] | Financial Services Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 74.00%
C000092936 [Member] | Energy Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000092935 [Member] | Xcel Energy Inc 6 25 10 15 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092935 [Member] | American AgCredit Corp 5 25 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092935 [Member] | BNP Paribas S A 8 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092935 [Member] | NextEra Energy Capital Holdings Inc Series U 6 50 06 01 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092935 [Member] | Hartford Insurance Group The Inc 6 04 02 12 47 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092935 [Member] | Land O Lakes Inc 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000092935 [Member] | Credit Agricole S A 7 13 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.50%
C000092935 [Member] | Barclays PLC 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.90%
C000092935 [Member] | Wells Fargo And Co Series L 7 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.10%
C000092935 [Member] | Bank of America Corp 6 63 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.60%
C000092935 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 15.40%
C000092935 [Member] | Industrial Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000092935 [Member] | Consumer Staples Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.50%
C000092935 [Member] | Consumer Discretionary Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092935 [Member] | Communications Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.50%
C000092935 [Member] | Real Estate Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092935 [Member] | Financial Services Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 74.00%
C000092935 [Member] | Energy Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000092934 [Member] | Xcel Energy Inc 6 25 10 15 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092934 [Member] | American AgCredit Corp 5 25 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092934 [Member] | BNP Paribas S A 8 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092934 [Member] | NextEra Energy Capital Holdings Inc Series U 6 50 06 01 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092934 [Member] | Hartford Insurance Group The Inc 6 04 02 12 47 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092934 [Member] | Land O Lakes Inc 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000092934 [Member] | Credit Agricole S A 7 13 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.50%
C000092934 [Member] | Barclays PLC 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.90%
C000092934 [Member] | Wells Fargo And Co Series L 7 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.10%
C000092934 [Member] | Bank of America Corp 6 63 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.60%
C000092934 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 15.40%
C000092934 [Member] | Industrial Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000092934 [Member] | Consumer Staples Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.50%
C000092934 [Member] | Consumer Discretionary Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092934 [Member] | Communications Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.50%
C000092934 [Member] | Real Estate Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092934 [Member] | Financial Services Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 74.00%
C000092934 [Member] | Energy Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000092933 [Member] | Xcel Energy Inc 6 25 10 15 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092933 [Member] | American AgCredit Corp 5 25 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092933 [Member] | BNP Paribas S A 8 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092933 [Member] | NextEra Energy Capital Holdings Inc Series U 6 50 06 01 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092933 [Member] | Hartford Insurance Group The Inc 6 04 02 12 47 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092933 [Member] | Land O Lakes Inc 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000092933 [Member] | Credit Agricole S A 7 13 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.50%
C000092933 [Member] | Barclays PLC 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.90%
C000092933 [Member] | Wells Fargo And Co Series L 7 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.10%
C000092933 [Member] | Bank of America Corp 6 63 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.60%
C000092933 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 15.40%
C000092933 [Member] | Industrial Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000092933 [Member] | Consumer Staples Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.50%
C000092933 [Member] | Consumer Discretionary Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092933 [Member] | Communications Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.50%
C000092933 [Member] | Real Estate Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092933 [Member] | Financial Services Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 74.00%
C000092933 [Member] | Energy Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000092932 [Member] | Xcel Energy Inc 6 25 10 15 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092932 [Member] | American AgCredit Corp 5 25 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.20%
C000092932 [Member] | BNP Paribas S A 8 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092932 [Member] | NextEra Energy Capital Holdings Inc Series U 6 50 06 01 85 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092932 [Member] | Hartford Insurance Group The Inc 6 04 02 12 47 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.30%
C000092932 [Member] | Land O Lakes Inc 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000092932 [Member] | Credit Agricole S A 7 13 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.50%
C000092932 [Member] | Barclays PLC 8 00 [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.90%
C000092932 [Member] | Wells Fargo And Co Series L 7 50 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.10%
C000092932 [Member] | Bank of America Corp 6 63 [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.60%
C000092932 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 15.40%
C000092932 [Member] | Industrial Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000092932 [Member] | Consumer Staples Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.50%
C000092932 [Member] | Consumer Discretionary Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092932 [Member] | Communications Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 4.50%
C000092932 [Member] | Real Estate Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000092932 [Member] | Financial Services Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 74.00%
C000092932 [Member] | Energy Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 1.40%
C000118178 [Member] | NR [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.70% [1]
C000118178 [Member] | Money Market Funds Quality [Member]  
Holdings [Line Items]  
Percent of Total Investments 7.60% [1]
C000118178 [Member] | Standard & Poor's, BBB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.00% [1]
C000118178 [Member] | Standard & Poor's, BB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 27.90% [1]
C000118178 [Member] | Standard & Poor's, B Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 50.50% [1]
C000118178 [Member] | Standard & Poor's, CCC Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 9.30% [1]
C000118178 [Member] | Money Market Funds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 7.60%
C000118178 [Member] | Common Stock [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
C000118178 [Member] | Corporate Bonds and Notes [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 57.50%
C000118178 [Member] | Senior Floating Rate Loan Interests [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 27.20%
C000118178 [Member] | Foreign Corporate Bonds and Notes [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.00%
C000118178 [Member] | Net Other Assets and Liabilities [Member]  
Holdings [Line Items]  
Percent of Net Asset Value (0.30%)
C000121471 [Member] | NR [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.70% [2]
C000121471 [Member] | Money Market Funds Quality [Member]  
Holdings [Line Items]  
Percent of Total Investments 7.60% [2]
C000121471 [Member] | Standard & Poor's, BBB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.00% [2]
C000121471 [Member] | Standard & Poor's, BB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 27.90% [2]
C000121471 [Member] | Standard & Poor's, B Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 50.50% [2]
C000121471 [Member] | Standard & Poor's, CCC Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 9.30% [2]
C000121471 [Member] | Money Market Funds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 7.60%
C000121471 [Member] | Common Stock [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
C000121471 [Member] | Corporate Bonds and Notes [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 57.50%
C000121471 [Member] | Senior Floating Rate Loan Interests [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 27.20%
C000121471 [Member] | Foreign Corporate Bonds and Notes [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.00%
C000121471 [Member] | Net Other Assets and Liabilities [Member]  
Holdings [Line Items]  
Percent of Net Asset Value (0.30%)
C000121472 [Member] | NR [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.70% [3]
C000121472 [Member] | Money Market Funds Quality [Member]  
Holdings [Line Items]  
Percent of Total Investments 7.60% [3]
C000121472 [Member] | Standard & Poor's, BBB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.00% [3]
C000121472 [Member] | Standard & Poor's, BB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 27.90% [3]
C000121472 [Member] | Standard & Poor's, B Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 50.50% [3]
C000121472 [Member] | Standard & Poor's, CCC Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 9.30% [3]
C000121472 [Member] | Money Market Funds [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 7.60%
C000121472 [Member] | Common Stock [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
C000121472 [Member] | Corporate Bonds and Notes [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 57.50%
C000121472 [Member] | Senior Floating Rate Loan Interests [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 27.20%
C000121472 [Member] | Foreign Corporate Bonds and Notes [Member]  
Holdings [Line Items]  
Percent of Net Asset Value 8.00%
C000121472 [Member] | Net Other Assets and Liabilities [Member]  
Holdings [Line Items]  
Percent of Net Asset Value (0.30%)
C000232961 [Member] | NR [Member]  
Holdings [Line Items]  
Percent of Total Investments 11.90%
C000232961 [Member] | Standard & Poor's, BBB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 17.10%
C000232961 [Member] | Standard & Poor's, BB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.40%
C000232961 [Member] | Standard & Poor's, B Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.00%
C000232961 [Member] | Standard & Poor's, A Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 28.40%
C000232961 [Member] | Standard & Poor's, AA Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 33.40%
C000232961 [Member] | Standard & Poor's, AAA Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.80%
C000232961 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.40%
C000232961 [Member] | Gas [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.80%
C000232961 [Member] | Insured [Member]  
Holdings [Line Items]  
Percent of Total Investments 9.80%
C000232961 [Member] | Airport [Member]  
Holdings [Line Items]  
Percent of Total Investments 10.70%
C000232961 [Member] | Hospital [Member]  
Holdings [Line Items]  
Percent of Total Investments 11.50%
C000232961 [Member] | Unclassified Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 25.40%
C000232961 [Member] | Industrial Development Bond [Member]  
Holdings [Line Items]  
Percent of Total Investments 8.40%
C000232961 [Member] | Continuing Care Retirement Communities [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.00%
C000232961 [Member] | Government Obligation Bond Unlimited Tax [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.10%
C000232961 [Member] | Certificates of Participation [Member]  
Holdings [Line Items]  
Percent of Total Investments 8.90%
C000232962 [Member] | NR [Member]  
Holdings [Line Items]  
Percent of Total Investments 11.90% [4]
C000232962 [Member] | Standard & Poor's, BBB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 17.10% [4]
C000232962 [Member] | Standard & Poor's, BB Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.40% [4]
C000232962 [Member] | Standard & Poor's, B Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 2.00% [4]
C000232962 [Member] | Standard & Poor's, A Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 28.40% [4]
C000232962 [Member] | Standard & Poor's, AA Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 33.40% [4]
C000232962 [Member] | Standard & Poor's, AAA Rating [Member]  
Holdings [Line Items]  
Percent of Total Investments 3.80% [4]
C000232962 [Member] | Utilities Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.40%
C000232962 [Member] | Gas [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.80%
C000232962 [Member] | Insured [Member]  
Holdings [Line Items]  
Percent of Total Investments 9.80%
C000232962 [Member] | Airport [Member]  
Holdings [Line Items]  
Percent of Total Investments 10.70%
C000232962 [Member] | Hospital [Member]  
Holdings [Line Items]  
Percent of Total Investments 11.50%
C000232962 [Member] | Unclassified Sector [Member]  
Holdings [Line Items]  
Percent of Total Investments 25.40%
C000232962 [Member] | Industrial Development Bond [Member]  
Holdings [Line Items]  
Percent of Total Investments 8.40%
C000232962 [Member] | Continuing Care Retirement Communities [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.00%
C000232962 [Member] | Government Obligation Bond Unlimited Tax [Member]  
Holdings [Line Items]  
Percent of Total Investments 6.10%
C000232962 [Member] | Certificates of Participation [Member]  
Holdings [Line Items]  
Percent of Total Investments 8.90%
[1] The ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). Investment grade is defined as those issuers that have a long-term credit rating of BBB- or higher. "NR" indicates no rating. The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
[2] The ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). Investment grade is defined as those issuers that have a long-term credit rating of BBB- or higher. "NR" indicates no rating. The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
[3] The ratings are by S&P Global Ratings. A credit rating is an assessment provided by a nationally recognized statistical rating organization (NRSRO) of the creditworthiness of an issuer with respect to debt obligations except for those debt obligations that are only privately rated. Ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). Investment grade is defined as those issuers that have a long-term credit rating of BBB- or higher. "NR" indicates no rating. The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.
[4] The credit quality and ratings information presented above reflect the ratings assigned by one or more nationally recognized statistical rating organizations (NRSROs), including S&P Global Ratings, Moody’s Investors Service, Inc., Fitch Ratings or a comparably rated NRSRO. For situations in which a security is rated by more than one NRSRO and the ratings are not equivalent, the highest rating is used. Sub-investment grade ratings are those rated BB+/Ba1 or lower. Investment grade ratings are those rated BBB-/Baa3 or higher. “NR” indicates no rating. The credit ratings shown relate to the creditworthiness of the issuers of the underlying securities in the Fund, and not to the Fund or its shares. Credit ratings are subject to change.