Mortgage Banking Activity - Residential Mortgage Loans (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance at beginning of period	$ 1,172
Balance at end of period	1,014	$ 1,172
Mortgage loans
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance at beginning of period	250	409
Originations and purchases	485	2,836
Sales, net of gains	(551)	(3,025)
Mortgage loans transferred from (to) held for investment	0	30
Balance at end of period	$ 184	$ 250