Regulatory Capital and Other Regulatory Matters (Common Share Repurchases) (Details) - USD ($)			3 Months Ended			9 Months Ended
		Oct. 05, 2021	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jul. 12, 2021	Mar. 31, 2021	Jan. 11, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Accelerated Share Repurchases [Line Items]
Treasury stock, common, amount			$ 679,000,000	$ 502,000,000	$ 1,000,000	$ 679,000,000	$ 1,000,000		$ 219,000,000		$ 1,000,000	$ 0	$ 104,000,000
Treasury stock, common, shares (in shares)			13,055,000	9,641,000	9,000	13,055,000	9,000		5,276,000		37,000	53,000	3,838,000
Common stock, shares outstanding (in shares)			349,598,889	362,639,000	373,857,000	349,598,889	373,857,000		371,805,000		374,674,415	373,837,000	373,155,000	374,332,000
Dividends declared (in dollars per share)			$ 0.25	$ 0.19	$ 0.19	$ 0.25	$ 0.19		$ 0.19		$ 0.19	$ 0.19	$ 0.19
Cash dividends declared per common share (in dollars per share)	[1]		$ 0.25		$ 0.19	$ 0.63	$ 0.57
Common stock
Accelerated Share Repurchases [Line Items]
Stock repurchase program, authorized amount								$ 2,000,000,000		$ 1,600,000,000
Common stock | Subsequent event
Accelerated Share Repurchases [Line Items]
Dividends payable, date declared		Oct. 05, 2021
Cash dividends declared per common share (in dollars per share)		$ 0.25
Dividends payable, date to be paid		Nov. 15, 2021
Dividends payable, date of record		Nov. 01, 2021
Series B Preferred Stock
Accelerated Share Repurchases [Line Items]
Gross proceeds from issuance of series preferred stock				$ 1,350,000,000
Series C Preferred Stock
Accelerated Share Repurchases [Line Items]
Gross proceeds from issuance of series preferred stock				$ 1,000,000,000

[1] Figures in the table may not recalculate exactly due to rounding. Earnings per share is calculated based on unrounded numbers.