Components of Other Comprehensive Income (Loss) - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 8,494	$ 8,307
Net unrealized gains (losses)	(424)	(102)
Amounts reclassified from AOCI	0	1
Other comprehensive income (loss)	(424)	(101)
Balance, end of period	8,696	8,307
Securities AFS
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(36)	108
Net unrealized gains (losses)	(404)	(103)
Amounts reclassified from AOCI	0	0
Other comprehensive income (loss)	(404)	(103)
Balance, end of period	(440)	5
Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	3	12
Net unrealized gains (losses)	(20)	(1)
Amounts reclassified from AOCI	(1)	(1)
Other comprehensive income (loss)	(21)	(2)
Balance, end of period	(18)	10
Pension and Post-retirement Plans
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(255)	(260)
Net unrealized gains (losses)	0	2
Amounts reclassified from AOCI	1	2
Other comprehensive income (loss)	1	4
Balance, end of period	(254)	(256)
Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(288)	(140)
Balance, end of period	$ (712)	$ (241)