Shareholders' Equity - Schedule of Dividends Declared (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Dividends Payable [Line Items]
Preferred stock cash dividend	$ 55	$ 50	$ 55	$ 55	$ 36	$ 55	$ 160	$ 146
Cash dividends declared (in USD per share)	$ 0.52	$ 0.47	$ 0.47	$ 0.47	$ 0.42	$ 0.42	$ 1.46	$ 1.31
Common stock dividends	$ 189	$ 175	$ 177	$ 179	$ 153	$ 154	$ 541	$ 486
Series C Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,313			$ 1,313			$ 3,939	$ 3,939
Preferred stock cash dividend	$ 6			$ 6			$ 19	$ 19
Series C Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.33			$ 0.33			$ 0.99	$ 0.99
Series D Preferred Stock
Dividends Payable [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 D Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.37			$ 0.37			$ 1.11	$ 1.11
Series E Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,500			$ 1,500			$ 4,500	$ 4,500
Preferred stock cash dividend	$ 11			$ 11			$ 33	$ 33
Series E Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.38			$ 0.38			$ 1.14	$ 1.14
Series F Preferred Stock
Dividends Payable [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 F Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 26.25			$ 26.25			$ 52.50	$ 52.50
Series G Preferred Stock
Dividends Payable [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 G Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.33			$ 0.33			$ 0.99	$ 0.99
Series H Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0			$ 0			$ 2,813	$ 0
Preferred stock cash dividend	$ 0			$ 0			$ 14	$ 0
Series H Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0			$ 0			$ 28.13	$ 0