Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred stock	Common stock	Accumulated paid-in capital	Retained earnings	Retained earnings Cumulative Effect, Period of Adoption, Adjustment	Accumulated other comprehensive income (loss)
Balance at beginning of period at Dec. 31, 2018	$ 7,578	$ (3)	$ 566	$ 0	$ 3,806	$ 3,456	$ (3)	$ (250)
Balance at beginning of period (in shares) at Dec. 31, 2018				187,554,000
Net income for the period	633					633
Other comprehensive loss, net of tax	299							299
Bank common stock repurchased (in shares)				(18,001,000)
Bank common stock repurchased	(826)				(826)
Net shares issued from stock warrant exercises (in shares)				8,000
Net activity under employee plans and related tax benefits (in shares)				812,000
Net activity under employee plans and related tax benefits	22				22
Dividends on preferred stock	(25)					(25)
Dividends on common stock	$ (169)					(169)
Dividends on common stock (in dollars per share)	$ 0.94
Balance at end of period at Sep. 30, 2019	$ 7,509		566	$ 0	3,002	3,892		49
Balance at end of period (in shares) at Sep. 30, 2019				170,373,000
Balance at beginning of period at Dec. 31, 2018	$ 7,578	(3)	566	$ 0	3,806	3,456	(3)	(250)
Balance at beginning of period (in shares) at Dec. 31, 2018				187,554,000
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Balance at end of period at Dec. 31, 2019	$ 7,353	20	566	$ 0	2,735	4,009	20	43
Balance at end of period (in shares) at Dec. 31, 2019	165,057,000			165,057,000
Balance at beginning of period at Jun. 30, 2019	$ 7,599		566	$ 0	3,271	3,737		25
Balance at beginning of period (in shares) at Jun. 30, 2019				176,935,000
Net income for the period	222					222
Other comprehensive loss, net of tax	24							24
Bank common stock repurchased (in shares)				(6,638,000)
Bank common stock repurchased	(275)				(275)
Net activity under employee plans and related tax benefits (in shares)				76,000
Net activity under employee plans and related tax benefits	6				6
Dividends on preferred stock	(8)					(8)
Dividends on common stock	$ (60)					(60)
Dividends on common stock (in dollars per share)	$ 0.34
Change in deferred compensation	$ 1					1
Balance at end of period at Sep. 30, 2019	7,509		566	$ 0	3,002	3,892		49
Balance at end of period (in shares) at Sep. 30, 2019				170,373,000
Balance at beginning of period at Dec. 31, 2019	$ 7,353	$ 20	566	$ 0	2,735	4,009	$ 20	43
Balance at beginning of period (in shares) at Dec. 31, 2019	165,057,000			165,057,000
Net income for the period	$ 255					255
Other comprehensive loss, net of tax	$ 289							289
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Bank common stock repurchased (in shares)				(1,680,000)
Bank common stock repurchased	$ (75)				(75)
Net shares issued from stock warrant exercises (in shares)				1,000
Net activity under employee plans and related tax benefits (in shares)				631,000
Net activity under employee plans and related tax benefits	20				20
Dividends on preferred stock	(25)					(25)
Dividends on common stock	$ (169)					(169)
Dividends on common stock (in dollars per share)	$ 1.02
Balance at end of period at Sep. 30, 2020	$ 7,668		566	$ 0	2,680	4,090		332
Balance at end of period (in shares) at Sep. 30, 2020	164,009,000			164,009,000
Balance at beginning of period at Jun. 30, 2020	$ 7,575		566	$ 0	2,675	3,979		355
Balance at beginning of period (in shares) at Jun. 30, 2020				163,978,000
Net income for the period	175					175
Other comprehensive loss, net of tax	(23)							(23)
Net activity under employee plans and related tax benefits (in shares)				31,000
Net activity under employee plans and related tax benefits	5				5
Dividends on preferred stock	(9)					(9)
Dividends on common stock	$ (56)					(56)
Dividends on common stock (in dollars per share)	$ 0.34
Change in deferred compensation	$ 1					1
Balance at end of period at Sep. 30, 2020	$ 7,668		$ 566	$ 0	$ 2,680	$ 4,090		$ 332
Balance at end of period (in shares) at Sep. 30, 2020	164,009,000			164,009,000