Capital Preferred Stock (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 2,025		$ 2,475	$ 1,225
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	172		172	172
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	103		103	103
Series E Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 0	[1]	450	450
Stock Redeemed or Called During Period, Shares	4,500
Series F Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 500		500	500
Series G Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	750		750	0
Series H Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 500		$ 500	$ 0

[1] All 4,500 shares of outstanding Series E Preferred Stock were redeemed in the first quarter of 2018.