Regulatory Capital and Other Regulatory Matters (Common Share Repurchases) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
	Jul. 14, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Accelerated Share Repurchases [Line Items]
Treasury stock, common, amount		$ 0	$ 229	$ 0	$ 229	$ 104	$ 299	$ 300	$ 211
Treasury stock, common, shares		53,000	7,775,000	53,000	7,775,000	3,838,000	9,554,000	9,287,000	8,113,000
Common stock, shares outstanding		373,837,123	392,775,000	373,837,123	392,775,000	373,155,000	374,331,998	383,523,000	399,761,000	404,900,000
Dividends declared, amount per common share		$ 0.19	$ 0.17	$ 0.19	$ 0.17	$ 0.19	$ 0.17	$ 0.17	$ 0.17
Cash dividends declared per common share		$ 0.19	$ 0.17	$ 0.38	$ 0.34
Stock repurchase program, authorized amount			$ 1,250		$ 1,250
Common stock | Subsequent event
Accelerated Share Repurchases [Line Items]
Dividends Payable, Date Declared	Jul. 14, 2020
Cash dividends declared per common share	$ 0.19
Dividends Payable, Date to be Paid	Aug. 14, 2020
Dividends Payable, Date of Record	Jul. 31, 2020