Loans Held-for-Investment (Past Due Loans) (Details) - USD ($)
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Loans, Aging [Abstract]          
Total Past Due $ 48,000,000   $ 48,000,000   $ 80,000,000
Current 6,242,000,000   6,242,000,000   6,272,000,000
Total Investment Loans 6,290,000,000   6,290,000,000   6,352,000,000
Loans greater than 90 days past due accounted for under the fair value option 12,000,000   12,000,000   10,000,000
Accrued interest on nonaccrual loans 1,000,000 $ 1,000,000 2,000,000 $ 4,000,000  
90 Days and Still Accruing 0   0   0
Residential first mortgage          
Loans, Aging [Abstract]          
Total Past Due 34,000,000   34,000,000   63,000,000
Current 2,102,000,000   2,102,000,000   3,037,000,000
Total Investment Loans 2,136,000,000   2,136,000,000   3,100,000,000
Second mortgage          
Loans, Aging [Abstract]          
Total Past Due 4,000,000   4,000,000   2,000,000
Current 123,000,000   123,000,000   133,000,000
Total Investment Loans 127,000,000   127,000,000   135,000,000
HELOC commitments          
Loans, Aging [Abstract]          
Total Past Due 8,000,000   8,000,000   12,000,000
Current 318,000,000   318,000,000   372,000,000
Total Investment Loans 326,000,000   326,000,000   384,000,000
Other          
Loans, Aging [Abstract]          
Total Past Due 2,000,000   2,000,000   1,000,000
Current 28,000,000   28,000,000   30,000,000
Total Investment Loans 30,000,000   30,000,000   31,000,000
Consumer loans          
Loans, Aging [Abstract]          
Total Past Due 48,000,000   48,000,000   78,000,000
Current 2,571,000,000   2,571,000,000   3,572,000,000
Total Investment Loans 2,619,000,000   2,619,000,000   3,650,000,000
Commercial real estate          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
Current 1,168,000,000   1,168,000,000   814,000,000
Total Investment Loans 1,168,000,000   1,168,000,000   814,000,000
Commercial and industrial          
Loans, Aging [Abstract]          
Total Past Due 0   0   2,000,000
Current 708,000,000   708,000,000   550,000,000
Total Investment Loans 708,000,000   708,000,000   552,000,000
Warehouse lending          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
Current 1,795,000,000   1,795,000,000   1,336,000,000
Total Investment Loans 1,795,000,000   1,795,000,000   1,336,000,000
Commercial loans          
Loans, Aging [Abstract]          
Total Past Due 0   0   2,000,000
Current 3,671,000,000   3,671,000,000   2,700,000,000
Total Investment Loans 3,671,000,000   3,671,000,000   2,702,000,000
30-59 Days Past Due          
Loans, Aging [Abstract]          
Total Past Due 6,000,000   6,000,000   10,000,000
30-59 Days Past Due | Residential first mortgage          
Loans, Aging [Abstract]          
Total Past Due 4,000,000   4,000,000   7,000,000
30-59 Days Past Due | Second mortgage          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
30-59 Days Past Due | HELOC commitments          
Loans, Aging [Abstract]          
Total Past Due 1,000,000   1,000,000   2,000,000
30-59 Days Past Due | Other          
Loans, Aging [Abstract]          
Total Past Due 1,000,000   1,000,000   1,000,000
30-59 Days Past Due | Consumer loans          
Loans, Aging [Abstract]          
Total Past Due 6,000,000   6,000,000   10,000,000
30-59 Days Past Due | Commercial real estate          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
30-59 Days Past Due | Commercial and industrial          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
30-59 Days Past Due | Warehouse lending          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
30-59 Days Past Due | Commercial loans          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
60-89 Days Past Due          
Loans, Aging [Abstract]          
Total Past Due 2,000,000   2,000,000   4,000,000
60-89 Days Past Due | Residential first mortgage          
Loans, Aging [Abstract]          
Total Past Due 1,000,000   1,000,000   3,000,000
60-89 Days Past Due | Second mortgage          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
60-89 Days Past Due | HELOC commitments          
Loans, Aging [Abstract]          
Total Past Due 0   0   1,000,000
60-89 Days Past Due | Other          
Loans, Aging [Abstract]          
Total Past Due 1,000,000   1,000,000   0
60-89 Days Past Due | Consumer loans          
Loans, Aging [Abstract]          
Total Past Due 2,000,000   2,000,000   4,000,000
60-89 Days Past Due | Commercial real estate          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
60-89 Days Past Due | Commercial and industrial          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
60-89 Days Past Due | Warehouse lending          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
60-89 Days Past Due | Commercial loans          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
90 Days or Greater Past Due          
Loans, Aging [Abstract]          
Total Past Due 40,000,000   40,000,000   66,000,000
90 Days or Greater Past Due | Residential first mortgage          
Loans, Aging [Abstract]          
Total Past Due 29,000,000   29,000,000   53,000,000
90 Days or Greater Past Due | Second mortgage          
Loans, Aging [Abstract]          
Total Past Due 4,000,000   4,000,000   2,000,000
90 Days or Greater Past Due | HELOC commitments          
Loans, Aging [Abstract]          
Total Past Due 7,000,000   7,000,000   9,000,000
90 Days or Greater Past Due | Other          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
90 Days or Greater Past Due | Consumer loans          
Loans, Aging [Abstract]          
Total Past Due 40,000,000   40,000,000   64,000,000
90 Days or Greater Past Due | Commercial real estate          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
90 Days or Greater Past Due | Commercial and industrial          
Loans, Aging [Abstract]          
Total Past Due 0   0   2,000,000
90 Days or Greater Past Due | Warehouse lending          
Loans, Aging [Abstract]          
Total Past Due 0   0   0
90 Days or Greater Past Due | Commercial loans          
Loans, Aging [Abstract]          
Total Past Due $ 0   $ 0   $ 2,000,000