N R not rated [Member] BB or Lower [Member] Bloomberg 7 Year Municipal Bond Index [Member] Bloomberg Municipal Bond Index [Member] C000048022 [Member] Common Shares Municipal Bonds [Member] Standard & Poor's, BBB Rating [Member] Standard & Poor's, A Rating [Member] Standard & Poor's, AA Rating [Member] Standard & Poor's, AAA Rating [Member] CANADA FINLAND FRANCE GERMANY JAPAN KOREA, REPUBLIC OF MAURITIUS NETHERLANDS UNITED ARAB EMIRATES UNITED KINGDOM UNITED STATES Corporate Bond Securities [Member] US Government Corporations and Agencies Securities [Member] Asset-Backed Securities [Member] Collateralized Mortgage-Backed Securities [Member] C000219780 [Member] Bloomberg U S Aggregate Bond Index [Member] Emerging Market Debt and Foreign Corporate Bonds [Member] Investments Purchased with Collateral from Securities Lending [Member] Supranational [Member] Other [Member] N A not applicable [Member] TÜRKIYE Turkey JP Morgan EMBI Global Diversified Index [Member] C000238439 [Member] Sovereign Debt [Member] SOUTH AFRICA SAUDI ARABIA ROMANIA POLAND PERU OMAN NIGERIA MEXICO INDONESIA INDIA HUNGARY CHILE BRAZIL SPAIN SWITZERLAND Exchange Traded Funds [Member] Common Stock [Member] C000238440 [Member] ICE BofA BB B U S Cash Pay High Yield Constrained Index [Member] Preferred Securities and Income Managed Accounts Portfolio Blended Benchmark [Member] ICE US Institutional Capital Securities Index [Member] C000238441 [Member] C000238442 [Member] Bloomberg U S Securitized Index [Member] SIFMA Municipal Swap Index [Member] S And P Municipal Bond Index [Member] C000248080 [Member] Investment Type [Axis] Net Assets Investment Company Portfolio Turnover No Trading Symbol Flag