Shareholders' Equity - Schedule of Dividends Declared (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Dividends Payable [Line Items]
Preferred stock cash dividend	$ 55	$ 55
Cash dividends declared (in USD per share)	$ 0.47	$ 0.42
Common stock dividends	$ 177	$ 154
Series C Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,313	$ 1,313
Preferred stock cash dividend	$ 6	$ 6
Series C Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.33	$ 0.33
Series D Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,475	$ 1,475
Preferred stock cash dividend	$ 11	$ 11
Series D Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.37	$ 0.37
Series E Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,500	$ 1,500
Preferred stock cash dividend	$ 11	$ 11
Series E Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.38	$ 0.38
Series F Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 2,625	$ 2,625
Preferred stock cash dividend	$ 20	$ 20
Series F Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 26.25	$ 26.25
Series G Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,338	$ 1,338
Preferred stock cash dividend	$ 7	$ 7
Series G Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.33	$ 0.33
Series H Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0	$ 0
Preferred stock cash dividend	$ 0	$ 0
Series H Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0	$ 0