Equity (Preferred Stock) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 10, 2020	Jan. 15, 2020	Jun. 04, 2018	Mar. 20, 2018
Dividends Payable [Line Items]
Preferred Stock, Shares Authorized		200,000,000	200,000,000
Preferred Stock, Shares Issued		26,072,200	26,032,200
Preferred Stock, Shares Outstanding		26,072,200	26,032,200
Preferred Stock
Preferred stock, dividends		$ 202,000,000	$ 178,000,000	$ 141,000,000
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	$ 1.017	$ 1.015
Preferred stock, dividends		$ 24,000,000	$ 24,000,000	$ 25,000,000
Fixed-to-Floating Rate Non-Cumulative Preferred Stock, Series C, par value $0.01
Dividends Payable [Line Items]
Preferred Stock, Dividend Payment Rate, Variable		5.25% Fixed-to-Floating Rate
Preferred Stock, Shares Authorized		1,500,000	1,500,000
Preferred Stock, Shares Issued		500,000	1,500,000
Preferred Stock, Shares Outstanding		500,000	1,500,000
Preferred Stock
Preferred Stock, Dividends Per Share, Declared		$ 45.860	$ 52.500	$ 52.500
Preferred stock, dividends		$ 59,000,000	$ 79,000,000	$ 79,000,000
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
Preferred Stock, Shares Authorized		500,000	500,000
Preferred Stock, Shares Issued		500,000	500,000					500,000
Preferred Stock, Shares Outstanding		500,000	500,000
Preferred Stock
Preferred Stock, Dividends Per Share, Declared		$ 58.750	$ 58.750	$ 28.233
Preferred stock, dividends		$ 30,000,000	$ 30,000,000	$ 14,000,000
Series E Preferred Stock [Member]
Dividends Payable [Line Items]
Preferred Stock, Shares Authorized		32,200	32,200
Preferred Stock, Shares Issued		32,200	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	$ 746.094
Preferred stock, dividends		$ 45,000,000	$ 45,000,000	$ 23,000,000
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		159,327,800	160,367,800
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	0
Preferred Stock, Shares Issued		40,000	0			40,000
Preferred Stock, Shares Outstanding		40,000	0
Preferred Stock
Preferred Stock, Dividends Per Share, Declared		$ 1,088.542	$ 0	$ 0
Preferred stock, dividends		$ 44,000,000	$ 0	$ 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	0
Preferred Stock, Shares Issued		1,000,000	0		1,000,000
Preferred Stock, Shares Outstanding		1,000,000	0
Preferred Stock
Preferred Stock, Dividends Per Share, Declared		$ 0	$ 0	$ 0
Preferred stock, dividends		$ 0	$ 0	$ 0