Parent Company Financial Information - Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income attributable to controlling interest	$ 999	$ 845	$ 441
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation, amortization, and other	28	46	65
Deferred income tax expense (benefit)	0	(18)	14
Stock-based compensation expense	43	32	22
Loss on extinguishment of debt	26	0	0
Total adjustments	(269)	(685)	378
Net cash provided by (used in) operating activities	741	172	830
Securities:
Proceeds from sales and prepayments of securities	68	629	192
Purchases of securities
Net cash provided by (used in) investing activities	(4,617)	(4,967)	(2,390)
Preferred stock:
Proceeds from issuance of preferred stock	145	144	0
Call of preferred stock	(100)	0	0
Cash dividends paid - preferred stock	(33)	(17)	(6)
Common stock:
Stock options exercised	28	7	9
Cash dividends paid	(333)	(222)	(171)
Repurchase of shares	(416)	(4)	(134)
Term borrowings:
Repayment of term borrowings	(108)	(327)	(396)
Net cash provided by (used in) financing activities	4,016	5,176	1,422
Net increase (decrease) in cash and cash equivalents	140	381	(138)
Cash and cash equivalents at beginning of period	1,648	1,267	1,405
Cash and cash equivalents at end of period	1,788	1,648	1,267
Total interest paid	170	261	411
Income taxes received from subsidiaries	258	105	71
Parent Company
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income attributable to controlling interest	999	845	441
Less undistributed net income of subsidiaries	340	740	158
Income before undistributed net income of subsidiaries	659	105	283
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation, amortization, and other	0	0	(1)
(Gain) loss on derivative transactions	0	4	0
Deferred income tax expense (benefit)	8	5	4
Stock-based compensation expense	43	32	22
Loss on extinguishment of debt	26	0	0
Other operating activities, net	(11)	21	28
Total adjustments	66	62	53
Net cash provided by (used in) operating activities	725	167	336
Securities:
Proceeds from sales and prepayments of securities	3	0	1
Purchases of securities
Purchases of securities	(10)	(5)	0
Sales (purchases) of premises and equipment	8	(2)	0
Cash received for business combination, net	0	103	0
Net cash provided by (used in) investing activities	1	96	1
Preferred stock:
Proceeds from issuance of preferred stock	145	144	0
Call of preferred stock	(100)	0	0
Cash dividends paid - preferred stock	(33)	(17)	(6)
Common stock:
Stock options exercised	28	7	9
Cash dividends paid	(333)	(222)	(171)
Repurchase of shares	(416)	(4)	(134)
Proceeds from issuance of term borrowings	0	795	0
Term borrowings:
Repayment of term borrowings	(120)	(500)	0
Other financing activities, net	0	(8)	0
Net cash provided by (used in) financing activities	(829)	195	(302)
Net increase (decrease) in cash and cash equivalents	(103)	458	35
Cash and cash equivalents at beginning of period	827	369	334
Cash and cash equivalents at end of period	724	827	369
Total interest paid	35	33	29
Income taxes received from subsidiaries	$ 28	$ 33	$ 43