Equity (Preferred Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020	Sep. 10, 2020	Jan. 15, 2020
Dividends Payable [Line Items]
Preferred Stock, Shares Authorized	200,000,000	200,000,000
Preferred Stock, Shares Issued	25,572,200	26,072,200
Preferred Stock, Shares Outstanding	25,572,200	26,072,200
Preferred Stock
Preferred stock, dividends	$ 195	$ 202	$ 178
Series A Preferred Stock [Member]
Dividends Payable [Line Items]
Preferred Stock, Dividend Payment Rate, Variable	Three-month LIBOR + 1.00%, with floor of 4.00%
Preferred Stock, Shares Authorized	27,600,000	27,600,000
Preferred Stock, Shares Issued	24,000,000	24,000,000
Preferred Stock, Shares Outstanding	24,000,000	24,000,000
Preferred Stock
Preferred Stock, Dividends Per Share, Declared	$ 1.015	$ 1.015	$ 1.017
Preferred stock, dividends	$ 24	$ 24	$ 24
Series C Preferred Stock [Member]
Dividends Payable [Line Items]
Preferred Stock, Shares Authorized	0	1,500,000		1,500,000
Preferred Stock, Shares Issued	0	500,000
Preferred Stock, Shares Outstanding	0	500,000
Preferred Stock
Preferred Stock, Dividends Per Share, Declared	$ 19.085	$ 45.860	$ 52.500
Preferred stock, dividends	$ 10	$ 59	$ 79
Fixed-to-Floating Rate Non-Cumulative Preferred Stock, Series D, par value $0.01
Dividends Payable [Line Items]
Preferred Stock, Dividend Payment Rate, Variable	5.875% Fixed-to-Floating Rate
Preferred Stock, Shares Authorized	500,000	500,000
Preferred Stock, Shares Issued	500,000	500,000
Preferred Stock, Shares Outstanding	500,000	500,000
Preferred Stock
Preferred Stock, Dividends Per Share, Declared	$ 58.750	$ 58.750	$ 58.750
Preferred stock, dividends	$ 29	$ 30	$ 30
Series E Preferred Stock [Member]
Dividends Payable [Line Items]
Preferred Stock, Dividend Payment Rate, Variable	5.625
Preferred Stock, Shares Authorized	32,200	32,200
Preferred Stock, Shares Issued	32,200	32,200
Preferred Stock, Shares Outstanding	32,200	32,200
Preferred Stock
Preferred Stock, Dividends Per Share, Declared	$ 1,406.252	$ 1,406.252	$ 1,406.252
Preferred stock, dividends	$ 45	$ 45	$ 45
Series A Junior Preferred Stock [Member]
Dividends Payable [Line Items]
Preferred Stock, Shares Authorized	10,000,000	10,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Not Designated Preferred Stock [Member]
Dividends Payable [Line Items]
Preferred Stock, Shares Authorized	160,827,800	159,327,800
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Depositary Shares, each representing a 1/1,000th interest in a share of 4.75% Non-Cumulative Preferred Stock, Series F
Dividends Payable [Line Items]
Preferred Stock, Shares Authorized	40,000	40,000
Preferred Stock, Shares Issued	40,000	40,000				40,000
Preferred Stock, Shares Outstanding	40,000	40,000
Preferred Stock
Preferred Stock, Dividends Per Share, Declared	$ 1,187.5	$ 1,088.542	$ 0
Preferred stock, dividends	$ 48	$ 44	$ 0
Fixed Rate Reset Non-Cumulative Preferred Stock, Series G, par value $0.01
Dividends Payable [Line Items]
Preferred Stock, Shares Authorized	1,000,000	1,000,000
Preferred Stock, Shares Issued	1,000,000	1,000,000			1,000,000
Preferred Stock, Shares Outstanding	1,000,000	1,000,000
Preferred Stock
Preferred Stock, Dividends Per Share, Declared	$ 39.035	$ 0	$ 0
Preferred stock, dividends	$ 39	$ 0	$ 0