Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Fair Value Measurements
Mortgage servicing rights	$ 679	$ 880	$ 1,020	$ 1,005
Other assets—Derivative assets, Total	49	26
Other liabilities-derivative liabilities, Total	13	2
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	(5)	(2)
Other liabilities-derivative liabilities, Cash Collateral and Netting	(13)	0
Recurring basis | MSR-related agreements
Fair Value Measurements
Other assets—Derivative assets, Cash Collateral and Netting	(105)	(23)
Other liabilities-derivative liabilities, Cash Collateral and Netting	8
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
Other liabilities-derivative liabilities	0
Recurring basis | Level Two
Fair Value Measurements
Mortgage loans held for sale	880	704
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	8	3
Other liabilities-derivative liabilities	18	2
Recurring basis | Level Two | MSR-related agreements
Fair Value Measurements
Other assets—Derivative assets	112	27
Other liabilities-derivative liabilities	0
Recurring basis | Level Three
Fair Value Measurements
Mortgage loans held for sale	42	39
Mortgage servicing rights	679	880
Recurring basis | Level Three | Interest rate lock commitments
Fair Value Measurements
Other assets—Derivative assets	39	21
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
Other liabilities-derivative liabilities	0
Total | Recurring basis
Fair Value Measurements
Mortgage loans held for sale	922	743
Mortgage servicing rights	679	880
Total | Recurring basis | Interest rate lock commitments
Fair Value Measurements
Other assets—Derivative assets, Total	39	21
Total | Recurring basis | Forward delivery commitments
Fair Value Measurements
Other assets—Derivative assets, Total	3	1
Other liabilities-derivative liabilities, Total	5	2
Total | Recurring basis | MSR-related agreements
Fair Value Measurements
Other assets—Derivative assets, Total	7	$ 4
Other liabilities-derivative liabilities, Total	$ 8