Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value Measurements
Mortgage servicing rights	$ 880	$ 1,005	$ 1,279	$ 1,022
Other assets—Derivative assets, Total	26	33
Other liabilities-derivative liabilities, Total	2	7
Recurring basis | Interest rate lock commitments
Fair Value Measurements
Other assets—Derivative assets, Cash Collateral and Netting	0	0
Recurring basis | Forward delivery commitments
Fair Value Measurements
Other assets—Derivative assets, Cash Collateral and Netting	(2)	(2)
Other liabilities-derivative liabilities, Cash Collateral and Netting	0	(7)
Recurring basis | MSR-related agreements
Fair Value Measurements
Other assets—Derivative assets, Cash Collateral and Netting	(23)	(58)
Recurring basis | Level One
Fair Value Measurements
Mortgage loans held for sale	0	0
Mortgage servicing rights	0	0
Recurring basis | Level One | Interest rate lock commitments
Fair Value Measurements
Other assets—Derivative assets	0	0
Recurring basis | Level One | Forward delivery commitments
Fair Value Measurements
Other assets—Derivative assets	0	0
Other liabilities-derivative liabilities	0	0
Recurring basis | Level One | MSR-related agreements
Fair Value Measurements
Other assets—Derivative assets	0	0
Recurring basis | Level Two
Fair Value Measurements
Mortgage loans held for sale	704	873
Mortgage servicing rights	0	0
Recurring basis | Level Two | Interest rate lock commitments
Fair Value Measurements
Other assets—Derivative assets	0	0
Recurring basis | Level Two | Forward delivery commitments
Fair Value Measurements
Other assets—Derivative assets	3	5
Other liabilities-derivative liabilities	2	14
Recurring basis | Level Two | MSR-related agreements
Fair Value Measurements
Other assets—Derivative assets	27	66
Recurring basis | Level Three
Fair Value Measurements
Mortgage loans held for sale	39	42
Mortgage servicing rights	880	1,005
Recurring basis | Level Three | Interest rate lock commitments
Fair Value Measurements
Other assets—Derivative assets	21	22
Recurring basis | Level Three | Forward delivery commitments
Fair Value Measurements
Other assets—Derivative assets	0	0
Other liabilities-derivative liabilities	0	0
Recurring basis | Level Three | MSR-related agreements
Fair Value Measurements
Other assets—Derivative assets	0	0
Total | Recurring basis
Fair Value Measurements
Mortgage loans held for sale	743	915
Mortgage servicing rights	880	1,005
Total | Recurring basis | Interest rate lock commitments
Fair Value Measurements
Other assets—Derivative assets, Total	21	22
Total | Recurring basis | Forward delivery commitments
Fair Value Measurements
Other assets—Derivative assets, Total	1	3
Other liabilities-derivative liabilities, Total	2	7
Total | Recurring basis | MSR-related agreements
Fair Value Measurements
Other assets—Derivative assets, Total	$ 4	$ 8