Derivative Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative asset, Fair Value	$ 21	$ 52
Derivative liability, Fair Value	19
U.S. Treasury and euro dollar futures
Derivative [Line Items]
Derivative asset, Fair Value	10	18
Mortgage backed securities forwards
Derivative [Line Items]
Derivative asset, Fair Value		26
Derivative liability, Fair Value	13
Swap futures
Derivative [Line Items]
Derivative asset, Fair Value	4
Interest rate swaps
Derivative [Line Items]
Derivative asset, Fair Value	7	8
Derivative liability, Fair Value	6	6
Other assets
Derivative [Line Items]
Derivative asset, Notional Amount	7,829	5,844
Derivative asset, Fair Value	57	46
Other assets | U.S. Treasury and euro dollar futures
Derivative [Line Items]
Derivative asset, Notional Amount	552	2,530
Derivative asset, Fair Value	1	7
Other assets | Mortgage backed securities forwards
Derivative [Line Items]
Derivative asset, Notional Amount	35	161
Derivative asset, Fair Value	0	2
Other assets | Swap futures
Derivative [Line Items]
Derivative asset, Notional Amount	132
Derivative asset, Fair Value	3
Other assets | Rate lock commitments
Derivative [Line Items]
Derivative asset, Notional Amount	4,654	2,604
Derivative asset, Fair Value	33	31
Other assets | Forward agency and loan sales
Derivative [Line Items]
Derivative asset, Notional Amount	2,099	194
Derivative asset, Fair Value	14	0
Other assets | Interest rate swaps
Derivative [Line Items]
Derivative asset, Notional Amount	357	355
Derivative asset, Fair Value	6	6
Other liabilities
Derivative [Line Items]
Derivative liability, Notional Amount	3,784	3,865
Derivative liability, Fair Value	18	20
Other liabilities | U.S. Treasury and euro dollar futures
Derivative [Line Items]
Derivative liability, Notional Amount	414	687
Derivative liability, Fair Value	0	1
Other liabilities | Mortgage backed securities forwards
Derivative [Line Items]
Derivative liability, Notional Amount	135	367
Derivative liability, Fair Value	1	6
Other liabilities | Swap futures
Derivative [Line Items]
Derivative liability, Notional Amount	25
Derivative liability, Fair Value	1
Other liabilities | Rate lock commitments
Derivative [Line Items]
Derivative liability, Notional Amount	538	22
Derivative liability, Fair Value	3	0
Other liabilities | Forward agency and loan sales
Derivative [Line Items]
Derivative liability, Notional Amount	2,326	2,789
Derivative liability, Fair Value	7	$ 13
Other liabilities | Interest rate swaps
Derivative [Line Items]
Derivative liability, Notional Amount	346
Derivative liability, Fair Value	$ 6