Equity Equity (Preferred Stock Dividends) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Dividends Payable [Line Items]
Dividends, Preferred Stock, Cash	$ 35	$ 77	$ 103	$ 109
Series A Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 0.256	$ 0.253	$ 0.506	$ 0.506
Dividends, Preferred Stock, Cash	$ 6	$ 6	$ 12	$ 12
Series C Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 9.606	$ 26.250	$ 19.085	$ 26.250
Dividends, Preferred Stock, Cash	$ 5	$ 39	$ 10	$ 39
Series D Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 0	$ 0	$ 29.375	$ 29.375
Dividends, Preferred Stock, Cash	$ 0	$ 0	$ 15	$ 15
Series E Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 351.563	$ 351.563	$ 703.126	$ 703.126
Dividends, Preferred Stock, Cash	$ 12	$ 12	$ 23	$ 23
Series G Preferred Stock
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 0	$ 0	$ 19.785	$ 0
Dividends, Preferred Stock, Cash	$ 0	$ 0	$ 19	$ 0
Series F Preferred Stock [Member]
Dividends Payable [Line Items]
Preferred Stock, Dividends Per Share, Declared	$ 296.875	$ 494.792	$ 593.750	$ 494.792
Dividends, Preferred Stock, Cash	$ 12	$ 20	$ 24	$ 20