Regulatory Capital and Other Regulatory Matters (Common Share Repurchases) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	Oct. 06, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Accelerated Share Repurchases [Line Items]
Treasury stock, common, amount		$ 1	$ 300	$ 1	$ 300	$ 0	$ 104	$ 299	$ 229	$ 211
Treasury stock, common, shares		9,000	9,287,000	9,000	9,287,000	53,000	3,838,000	9,554,000	7,775,000	8,113,000
Common stock, shares outstanding		373,857,264	383,523,000	373,857,264	383,523,000	373,837,000	373,155,000	374,331,998	392,775,000	399,761,000	404,900,000
Dividends declared, amount per common share		$ 0.19	$ 0.17	$ 0.19	$ 0.17	$ 0.19	$ 0.19	$ 0.17	$ 0.17	$ 0.17
Cash dividends declared per common share		$ 0.19	$ 0.17	$ 0.57	$ 0.51
Stock repurchase program, authorized amount			$ 1,250		$ 1,250
Common stock | Subsequent event
Accelerated Share Repurchases [Line Items]
Dividends Payable, Date Declared	Oct. 06, 2020
Cash dividends declared per common share	$ 0.19
Dividends Payable, Date to be Paid	Nov. 13, 2020
Dividends Payable, Date of Record	Oct. 30, 2020