Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended						9 Months Ended
	Oct. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Class of Stock [Line Items]
Preferred stock cash dividend		$ 38	$ 32	$ 44	$ 55	$ 50	$ 55	$ 114	$ 160
Series D Preferred Stock
Class of Stock [Line Items]
Preferred dividends declared (USD per share)		$ 1,475			$ 1,475			$ 4,425	$ 4,425
Preferred stock cash dividend		$ 11			$ 11			$ 33	$ 33
Series F Preferred Stock
Class of Stock [Line Items]
Preferred dividends declared (USD per share)		$ 2,625			$ 2,625			$ 5,250	$ 5,250
Preferred stock cash dividend		$ 20			$ 20			$ 40	$ 40
Series G Preferred Stock
Class of Stock [Line Items]
Preferred dividends declared (USD per share)		$ 1,338			$ 1,338			$ 4,014	$ 4,014
Preferred stock cash dividend		$ 7			$ 7			$ 21	$ 21
Series H Preferred Stock
Class of Stock [Line Items]
Preferred dividends declared (USD per share)		$ 0			$ 0			$ 2,813	$ 2,813,000,000
Preferred stock cash dividend		$ 0			$ 0			$ 14	$ 14
Series D Preferred Stock, Depository Share
Class of Stock [Line Items]
Preferred dividends declared (USD per share)		$ 0.37			$ 0.37			$ 1.11	$ 1.11
Series F Preferred Stock, Depository Share
Class of Stock [Line Items]
Preferred dividends declared (USD per share)		26.25			26.25			52.50	52.50
Series G Preferred Stock, Depository Share
Class of Stock [Line Items]
Preferred dividends declared (USD per share)		0.33			0.33			0.99	0.99
Series H Preferred Stock, Depository Share
Class of Stock [Line Items]
Preferred dividends declared (USD per share)		$ 0			$ 0			$ 28.13	$ 28,130,000
Subsequent Event | Series D Preferred Stock
Class of Stock [Line Items]
Preferred dividends declared (USD per share)	$ 1,475
Preferred stock cash dividend	$ 11
Subsequent Event | Series F Preferred Stock
Class of Stock [Line Items]
Preferred dividends declared (USD per share)	$ 973
Preferred stock cash dividend	$ 7
Subsequent Event | Series G Preferred Stock
Class of Stock [Line Items]
Preferred dividends declared (USD per share)	$ 1,338
Preferred stock cash dividend	$ 7
Subsequent Event | Series H Preferred Stock
Class of Stock [Line Items]
Preferred dividends declared (USD per share)	$ 2,813
Preferred stock cash dividend	$ 14
Subsequent Event | Series D Preferred Stock, Depository Share
Class of Stock [Line Items]
Preferred dividends declared (USD per share)	$ 0.37
Subsequent Event | Series F Preferred Stock, Depository Share
Class of Stock [Line Items]
Preferred dividends declared (USD per share)	9.73
Subsequent Event | Series G Preferred Stock, Depository Share
Class of Stock [Line Items]
Preferred dividends declared (USD per share)	0.33
Subsequent Event | Series H Preferred Stock, Depository Share
Class of Stock [Line Items]
Preferred dividends declared (USD per share)	$ 28.13