Equity Equity (Preferred Stock Dividends) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Dividends Payable [Line Items]
Dividends, Preferred Stock, Cash	$ 63	$ 59	$ 166	$ 168
Series A Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 0.256	$ 0.256	$ 0.762	$ 0.762
Dividends, Preferred Stock, Cash	$ 6	$ 6	$ 18	$ 18
Series C Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 0	$ 9.940	$ 19.085	$ 36.190
Dividends, Preferred Stock, Cash	$ 0	$ 15	$ 10	$ 54
Series D Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 29.375	$ 29.375	$ 58.750	$ 58.750
Dividends, Preferred Stock, Cash	$ 14	$ 15	$ 29	$ 30
Series E Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 351.563	$ 351.563	$ 1,054.689	$ 1,054.689
Dividends, Preferred Stock, Cash	$ 11	$ 11	$ 34	$ 34
Series G Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 19.250	$ 0	$ 39.035	$ 0
Dividends, Preferred Stock, Cash	$ 20	$ 0	$ 39	$ 0
Series F Preferred Stock [Member]
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 296.875	$ 296.875	$ 890.625	$ 791.667
Dividends, Preferred Stock, Cash	$ 12	$ 12	$ 36	$ 32