Fair Value Measurements - Roll Forward of Financial Instruments Classified as Level 3 (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Liabilities
Unrealized gains (losses) recorded in OCI	$ 0	$ 0
Recurring | Level 3
Assets
Balance at Beginning of Period	394,000,000	317,000,000	$ 327,000,000	$ 312,000,000
Total Gains (Losses) Recorded in Earnings	43,000,000	(29,000,000)	76,000,000	(38,000,000)
Purchases / Originations	393,000,000	179,000,000	596,000,000	296,000,000
Sales	(10,000,000)	0	(46,000,000)	(45,000,000)
Settlement	0	0	0	0
Transfers Out	(352,000,000)	(99,000,000)	(485,000,000)	(157,000,000)
Balance at End of Period	468,000,000	368,000,000	468,000,000	368,000,000
Liabilities
Balance at Beginning of Period	(51,000,000)	(66,000,000)	(45,000,000)	(66,000,000)
Total unrealized gains/(losses) recorded in earnings	(11,000,000)	24,000,000	(17,000,000)	24,000,000
Purchases / Originations	0	0	0	0
Sales	0	0	0	0
Settlement	0	0	0	0
Transfers Out	0	0	0	0
Balance at End of Period	(62,000,000)	(42,000,000)	(62,000,000)	(42,000,000)
Recurring | Level 3 | Home equity
Assets
Balance at Beginning of Period	2,000,000	2,000,000	2,000,000	2,000,000
Total Gains (Losses) Recorded in Earnings	0	0	0	0
Purchases / Originations	0	0	0	0
Sales	0	0	0	0
Settlement	0	0	0	0
Transfers Out	0	0	0	0
Balance at End of Period	2,000,000	2,000,000	2,000,000	2,000,000
Recurring | Level 3 | Mortgage servicing rights
Assets
Balance at Beginning of Period	223,000,000	278,000,000	291,000,000	290,000,000
Total Gains (Losses) Recorded in Earnings	(36,000,000)	(59,000,000)	(108,000,000)	(93,000,000)
Purchases / Originations	84,000,000	97,000,000	124,000,000	164,000,000
Sales	(10,000,000)	0	(46,000,000)	(45,000,000)
Settlement	0	0	0	0
Transfers Out	0	0	0	0
Balance at End of Period	261,000,000	316,000,000	261,000,000	316,000,000
Recurring | Level 3 | Rate lock commitments
Assets
Balance at Beginning of Period	169,000,000	37,000,000	34,000,000	20,000,000
Total Gains (Losses) Recorded in Earnings	79,000,000	30,000,000	184,000,000	55,000,000
Purchases / Originations	309,000,000	82,000,000	472,000,000	132,000,000
Sales	0	0	0	0
Settlement	0	0	0	0
Transfers Out	(352,000,000)	(99,000,000)	(485,000,000)	(157,000,000)
Balance at End of Period	205,000,000	50,000,000	205,000,000	50,000,000
Recurring | Level 3 | DOJ Liability
Liabilities
Balance at Beginning of Period	(35,000,000)	(60,000,000)	(35,000,000)	(60,000,000)
Total unrealized gains/(losses) recorded in earnings	0	25,000,000	0	25,000,000
Purchases / Originations	0	0	0	0
Sales	0	0	0	0
Settlement	0	0	0	0
Transfers Out	0	0	0	0
Balance at End of Period	(35,000,000)	(35,000,000)	(35,000,000)	(35,000,000)
Recurring | Level 3 | Contingent consideration
Liabilities
Balance at Beginning of Period	(16,000,000)	(6,000,000)	(10,000,000)	(6,000,000)
Total unrealized gains/(losses) recorded in earnings	(11,000,000)	(1,000,000)	(17,000,000)	(1,000,000)
Purchases / Originations	0	0	0	0
Sales	0	0	0	0
Settlement	0	0	0	0
Transfers Out	0	0	0	0
Balance at End of Period	$ (27,000,000)	$ (7,000,000)	$ (27,000,000)	$ (7,000,000)