Regulatory Capital and Other Regulatory Matters (Common Share Repurchases) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Apr. 16, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Accelerated Share Repurchases [Line Items]
Treasury stock, common, amount		$ 104	$ 211	$ 299	$ 300	$ 229
Treasury stock, common, shares		3,838,000	8,113,000	9,554,000	9,287,000	7,775,000
Common stock, shares outstanding		373,154,910	399,761,000	374,331,998	383,523,000	392,775,000	404,900,000
Dividends declared, amount per common share		$ 0.19	$ 0.17	$ 0.17	$ 0.17	$ 0.17
Cash dividends declared per common share		$ 0.19	$ 0.17
Stock repurchase program, authorized amount		$ 1,250
Common stock | Subsequent event
Accelerated Share Repurchases [Line Items]
Dividends Payable, Date Declared	Apr. 16, 2020
Cash dividends declared per common share	$ 0.19
Dividends Payable, Date to be Paid	May 15, 2020