Equity (Preferred Stock Dividends) (Details) - USD ($) $ / shares in Units, $ in Millions						3 Months Ended		6 Months Ended		9 Months Ended
	Aug. 17, 2020	May 15, 2020	Feb. 14, 2020	Aug. 15, 2019	May 15, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Class of Stock [Line Items]
Preferred stock dividend declared						$ 17	$ 7	$ 14	$ 7
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock dividend declared per share	$ 412.50	$ 412.50	$ 412.50	$ 412.50	$ 412.50					$ 1,237.50	$ 825.00
Preferred stock dividend declared	$ 7	$ 7	$ 7	$ 7	$ 7					$ 21	$ 14
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock dividend declared per share	$ 595.31	$ 0	$ 0	$ 0	$ 0					$ 595.31	$ 0
Preferred stock dividend declared	$ 10	$ 0	$ 0	$ 0	$ 0					$ 10	$ 0