Loans Held-for-Investment (Impaired Loans) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Impaired Loans [Line Items]          
With no related allowance recorded, Recorded Investment $ 3   $ 3   $ 25
With no related allowance recorded, unpaid principal balance 2   2   22
With an allowance recorded, recorded investment 70   70   96
With an allowance recorded, unpaid principal balance 71   71   98
With an allowance recorded, related allowance 15   15   20
Total recorded investment 73   73   121
Total unpaid principal balance 73   73   120
Average Recorded Investment 74 $ 142 88 $ 209  
Interest Income Recognized 0 1 2 4  
Residential first mortgage          
Impaired Loans [Line Items]          
With no related allowance recorded, Recorded Investment 2   2   20
With no related allowance recorded, unpaid principal balance 1   1   20
With an allowance recorded, recorded investment 40   40   65
With an allowance recorded, unpaid principal balance 41   41   67
With an allowance recorded, related allowance 7   7   12
Total recorded investment 42   42   85
Total unpaid principal balance 42   42   87
Average Recorded Investment 43 96 55 172  
Interest Income Recognized 0 1 1 4  
Second mortgage          
Impaired Loans [Line Items]          
With an allowance recorded, recorded investment 26   26   28
With an allowance recorded, unpaid principal balance 26   26   28
With an allowance recorded, related allowance 6   6   6
Total recorded investment 26   26   28
Total unpaid principal balance 26   26   28
Average Recorded Investment 25 29 26 30  
Interest Income Recognized 0 0 1 0  
HELOC commitments          
Impaired Loans [Line Items]          
With an allowance recorded, recorded investment 4   4   3
With an allowance recorded, unpaid principal balance 4   4   3
With an allowance recorded, related allowance 2   2   1
Total recorded investment 4   4   3
Total unpaid principal balance 4   4   3
Average Recorded Investment 5 15 5 6  
Interest Income Recognized 0 0 0 0  
Commercial and industrial          
Impaired Loans [Line Items]          
With no related allowance recorded, Recorded Investment 1   1   5
With no related allowance recorded, unpaid principal balance 1   1   2
With an allowance recorded, related allowance 0   0   0
Total recorded investment 1   1   5
Total unpaid principal balance 1   1   2
Average Recorded Investment 1 2 2 1  
Interest Income Recognized 0 $ 0 0 $ 0  
Other consumer          
Impaired Loans [Line Items]          
With an allowance recorded, recorded investment 0   0   0
With an allowance recorded, unpaid principal balance 0   0   0
With an allowance recorded, related allowance 0   0   1
Total recorded investment 0   0   0
Total unpaid principal balance $ 0   $ 0   $ 0