Shareholders' Equity - Schedule of Dividends Declared (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Dividends Payable [Line Items]
Preferred stock cash dividend		$ 36	$ 33	$ 91	$ 82
Common Stock Dividends Declared (in USD per share)		$ 0.38	$ 0.34	$ 0.76	$ 0.68
Common Stock Dividends		$ 142	$ 133	$ 286	$ 268
Series C Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 1,313	$ 1,313	$ 2,626	$ 2,626
Preferred stock cash dividend		$ 7	$ 6	$ 13	$ 13
Series C Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 0.33	$ 0.33	$ 0.66	$ 0.66
Series D Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 1,475	$ 1,475	$ 2,950	$ 2,950
Preferred stock cash dividend		$ 11	$ 11	$ 22	$ 22
Series D Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 0.37	$ 0.37	$ 0.74	$ 0.74
Series E Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 1,500	$ 1,500	$ 3,000	$ 3,000
Preferred stock cash dividend		$ 11	$ 11	$ 22	$ 22
Series E Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 0.38	$ 0.38	$ 0.76	$ 0.76
Series F Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 0	$ 0	$ 2,625	$ 2,625
Preferred stock cash dividend		$ 0	$ 0	$ 20	$ 20
Series F Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 0	$ 0	$ 26.25	$ 26.25
Series G Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 1,338	$ 951	$ 2,676	$ 951
Preferred stock cash dividend		$ 7	$ 5	$ 14	$ 5
Series G Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)		$ 0.33	$ 0.24	$ 0.66	$ 0.24
Subsequent Event | Series C Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,313
Preferred stock cash dividend	$ 6
Subsequent Event | Series C Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.33
Subsequent Event | Series D Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,475
Preferred stock cash dividend	$ 11
Subsequent Event | Series D Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.37
Subsequent Event | Series E Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,500
Preferred stock cash dividend	$ 11
Subsequent Event | Series E Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.38
Subsequent Event | Series F Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 2,625
Preferred stock cash dividend	$ 20
Subsequent Event | Series F Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 26.25
Subsequent Event | Series G Preferred Stock
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 1,338
Preferred stock cash dividend	$ 7
Subsequent Event | Series G Preferred Stock, Depository Share
Dividends Payable [Line Items]
Preferred dividends declared (USD per share)	$ 0.33