Annual report pursuant to Section 13 and 15(d)

Variable Interest Entities (Key Terms of NMTC Transaction) (Details)

v3.8.0.1
Variable Interest Entities (Key Terms of NMTC Transaction) (Details) - Variable Interest Entity, Primary Beneficiary - USD ($)
$ in Millions
Dec. 22, 2017
Mar. 21, 2017
Dec. 11, 2012
Oct. 03, 2012
Aug. 30, 2011
NMTC 1          
Variable Interest Entity [Line Items]          
Loan Amount         $ 58.3
Interest Rate on Loan to Investment Fund         1.00%
NMTC 1 | Minimum          
Variable Interest Entity [Line Items]          
Interest Rate on Loan to Investment Fund         1.00%
NMTC 1 | Maximum          
Variable Interest Entity [Line Items]          
Interest Rate on Loan to Investment Fund         3.96%
NMTC 1 | US Bancorp Investment          
Variable Interest Entity [Line Items]          
Financial Support to Other Entity         $ 22.4
NMTC 1 | Loan to Unicom          
Variable Interest Entity [Line Items]          
Financial Support to Other Entity         $ 76.8
NMTC 2          
Variable Interest Entity [Line Items]          
Loan Amount       $ 37.7  
Interest Rate on Loan to Investment Fund       1.00%  
NMTC 2 | Minimum          
Variable Interest Entity [Line Items]          
Interest Rate on Loan to Investment Fund       0.71%  
NMTC 2 | Maximum          
Variable Interest Entity [Line Items]          
Interest Rate on Loan to Investment Fund       0.77%  
NMTC 2 | US Bancorp Investment          
Variable Interest Entity [Line Items]          
Financial Support to Other Entity       $ 17.5  
NMTC 2 | Loan to Unicom          
Variable Interest Entity [Line Items]          
Financial Support to Other Entity       $ 55.2  
NMTC 3          
Variable Interest Entity [Line Items]          
Loan Amount     $ 8.2    
Interest Rate on Loan to Investment Fund     1.00%    
NMTC 3 | US Bancorp Investment          
Variable Interest Entity [Line Items]          
Financial Support to Other Entity     $ 3.8    
NMTC 3 | Loan to Unicom          
Variable Interest Entity [Line Items]          
Interest Rate on Loan to Investment Fund     1.35%    
Financial Support to Other Entity     $ 12.0    
NMTC 4          
Variable Interest Entity [Line Items]          
Loan Amount   $ 6.7      
Interest Rate on Loan to Investment Fund   1.00%      
NMTC 4 | US Bancorp Investment          
Variable Interest Entity [Line Items]          
Financial Support to Other Entity   $ 3.3      
NMTC 4 | Loan to Unicom          
Variable Interest Entity [Line Items]          
Interest Rate on Loan to Investment Fund   0.73%      
Financial Support to Other Entity   $ 9.8      
NMTC 5          
Variable Interest Entity [Line Items]          
Loan Amount $ 10.4        
Interest Rate on Loan to Investment Fund 1.00%        
NMTC 5 | Minimum          
Variable Interest Entity [Line Items]          
Interest Rate on Loan to Investment Fund 0.67%        
NMTC 5 | Maximum          
Variable Interest Entity [Line Items]          
Interest Rate on Loan to Investment Fund 1.24%        
NMTC 5 | US Bancorp Investment          
Variable Interest Entity [Line Items]          
Financial Support to Other Entity $ 5.1        
NMTC 5 | Loan to Unicom          
Variable Interest Entity [Line Items]          
Financial Support to Other Entity $ 14.7