v3.26.3
Shareholder Report, Average Annual Return (Details)
 10 Months Ended 12 Months Ended 20 Months Ended 29 Months Ended 60 Months Ended 82 Months Ended 106 Months Ended 112 Months Ended 119 Months Ended
Jul. 31, 2026
Jul. 31, 2026
Jul. 31, 2026
Jul. 31, 2026
Jul. 31, 2026
Jul. 31, 2026
Jul. 31, 2026
Jul. 31, 2026
Jul. 31, 2026
C000173018 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent   2.98%     (0.10%)       1.61%
C000180107 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent   2.87%     1.48%     2.18%  
C000193700 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent   2.53%     (0.53%)   1.33%    
C000209930 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent   5.04%     3.35% 3.62%      
C000248461 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent   3.70%   4.41%          
C000248462 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent   5.61%   7.57%          
C000248463 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent   4.18%   4.73%          
C000255190 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent   5.61% 5.85%            
C000263343 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent 4.32%                
C000264202 [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NAV              
Average Annual Return, Percent 3.03%                
ICE BofA U S Broad Market Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   ICE BofA U.S. Broad Market Index              
Average Annual Return, Percent   2.72%     (0.40%)       1.45%
Bloomberg U S Aggregate Bond Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   Bloomberg U.S. Aggregate Bond Index              
Average Annual Return, Percent 0.28% 2.71% 2.86% 3.63% (0.40%) 0.77% 1.54% 1.70%  
ICE BofA Enhanced Yield U S Broad Bond Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   ICE BofA Enhanced Yield U.S. Broad Bond Index              
Average Annual Return, Percent   3.17%     0.18%       1.94%
Bloomberg 1 5 Year U S Aggregate Bond Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   Bloomberg 1‑5 Year U.S. Aggregate Bond Index              
Average Annual Return, Percent   3.17%     1.66%     2.10%  
NUSA Custom Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NUSA Custom Index              
Average Annual Return, Percent [1]   3.04%     1.62%     2.38%  
Bloomberg MSCI U S Aggregate ESG Select Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   Bloomberg MSCI U.S. Aggregate ESG Select Index              
Average Annual Return, Percent   2.70%     (0.37%)   1.54%    
Bloomberg U S High Yield Very Liquid Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   Bloomberg U.S. High Yield Very Liquid Index              
Average Annual Return, Percent   5.41%     3.87% 4.54%      
Bloomberg MSCI U S High Yield Very Liquid ESG Select Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   Bloomberg MSCI U.S. High Yield Very Liquid ESG Select Index              
Average Annual Return, Percent   5.53%     3.71% 3.99%      
ICE US Institutional Capital Securities Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   ICE US Institutional Capital Securities Index              
Average Annual Return, Percent   5.44%   7.52%          
NPFI Blended Benchmark [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   NPFI Blended Benchmark              
Average Annual Return, Percent   5.84%   8.23%          
ICE BofA U S 3 Month Treasury Bill Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   ICE BofA U.S. 3‑Month Treasury Bill Index              
Average Annual Return, Percent   3.82%   4.40%          
JP Morgan CLO A Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   JP Morgan CLO A Index              
Average Annual Return, Percent   5.72% 6.05%            
S And P UBS Leveraged Loan Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   S&P UBS Leveraged Loan Index              
Average Annual Return, Percent   4.27% 5.12%            
Bloomberg U S Securitized Bond Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   Bloomberg U.S. Securitized Bond Index              
Average Annual Return, Percent 1.14%                
ICE BofA BB B U S Cash Pay High Yield Constrained Index [Member]                  
Average Annual Return [Line Items]                  
Line Graph and Table Measure Name   ICE BofA BB‑B U.S. Cash Pay High Yield Constrained Index              
Average Annual Return, Percent 3.17%                
[1] The NUSA Custom Index is defined as the linked returns between the Bloomberg MSCI 1‑5 Year U.S. Aggregate ESG Select index (effective July 1, 2023) and the ICE BofA Enhanced Yield 1‑5 Year U.S. Broad Bond Index (through market close on June 30, 2023).