Holding Company Only Financial Statements (Condensed Unconsolidated Statements of Financial Condition) (Details) - USD ($)
$ in Millions
Jun. 30, 2016
Dec. 31, 2015
Jun. 30, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Assets [Abstract]            
Cash and cash equivalents $ 184 $ 208 $ 246 $ 136 $ 281 $ 953
Other assets 920 639   416    
Total assets 13,723 13,715   9,840    
Liabilities and Stockholders’ Equity            
Long-term debt 247 247   331    
Other liabilities 624 423   500    
Total liabilities 12,124 12,186   8,467    
Stockholders’ Equity            
Preferred Stock 267 267   267    
Common stock 1 1   1    
Additional paid in capital 1,491 1,486   1,482    
Accumulated other comprehensive income (19) 2   8 (5) (2)
Accumulated deficit (141) (227)   (385)    
Total stockholders’ equity 1,599 1,529 $ 1,451 1,373 1,426 1,160
Total liabilities and stockholders’ equity $ 13,723 13,715   9,840    
Parent Company            
Assets [Abstract]            
Cash and cash equivalents   37   46 $ 50 $ 56
Investment in subsidiaries   1,738   1,571    
Other assets   50   43    
Total assets   1,825   1,660    
Liabilities and Stockholders’ Equity            
Long-term debt   247   248    
Total interest paying liabilities   247   248    
Other liabilities   49   39    
Total liabilities   296   287    
Stockholders’ Equity            
Preferred Stock   267   267    
Common stock   1   1    
Additional paid in capital   1,486   1,482    
Accumulated other comprehensive income   2   8    
Accumulated deficit   (227)   (385)    
Total stockholders’ equity   1,529   1,373    
Total liabilities and stockholders’ equity   $ 1,825   $ 1,660