Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions								2 Months Ended	12 Months Ended
	Nov. 16, 2020	Aug. 17, 2020	May 15, 2020	Feb. 14, 2020	Nov. 15, 2019	Aug. 15, 2019	May 15, 2019	Feb. 16, 2021	Dec. 31, 2020	Dec. 31, 2019	Feb. 10, 2021	Feb. 06, 2020	May 03, 2019	Aug. 05, 2018
Subsequent Event [Line Items]
Preferred stock, aggregate dividends declared									$ 44	$ 21
Series A Preferred Stock
Subsequent Event [Line Items]
Preferred stock, dividends declared per share	$ 412.50	$ 412.50	$ 412.50	$ 412.50	$ 412.50	$ 412.50	$ 412.50		$ 1,650.00	$ 1,237.50
Preferred stock, aggregate dividends declared	$ 7	$ 7	$ 7	$ 7	$ 7	$ 7	$ 7		$ 28	$ 21
Series B Preferred Stock
Subsequent Event [Line Items]
Preferred stock, dividends declared per share	$ 421.88	$ 595.31	$ 0	$ 0	$ 0	$ 0	$ 0		$ 1,017.19	$ 0
Preferred stock, aggregate dividends declared	$ 6	$ 10	$ 0	$ 0	$ 0	$ 0	$ 0		$ 16	$ 0
Authorization Under 10b5-1 Plan
Subsequent Event [Line Items]
Stock repurchase program, authorized repurchase amount												$ 500	$ 400	$ 200
Subsequent Event
Subsequent Event [Line Items]
Preferred stock, aggregate dividends declared								$ 25
Subsequent Event | Series A Preferred Stock
Subsequent Event [Line Items]
Preferred stock, dividends declared per share								$ 412.50
Subsequent Event | Series B Preferred Stock
Subsequent Event [Line Items]
Preferred stock, dividends declared per share								421.88
Subsequent Event | Series C Preferred Stock
Subsequent Event [Line Items]
Preferred stock, dividends declared per share								$ 466.58
Subsequent Event | Authorization Under 10b5-1 Plan
Subsequent Event [Line Items]
Stock repurchase program, authorized repurchase amount											$ 200