Preferred Stock (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Preferred stock, shares outstanding (shares)		1,265	21,447,500
Amount Outstanding		$ 1,265	$ 1,265
6.0% Non-Cumulative Preferred Stock, Series I ($1,000,000 stated value)
Class of Stock [Line Items]
Preferred stock, shares outstanding (shares)		1,265
Dividend Rate		6.00%
Amount Outstanding		$ 1,265	0
Floating Rate Non-Cumulative Preferred Stock, Series F ($25 stated value) [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (shares)		0
Dividend Rate		0.00%
Amount Outstanding		$ 0	517
14,950,000 Depositary Shares each representing a one-fortieth interest in a share of Floating Rate Non-Cumulative Preferred Stock, Series G ($1,000 stated value) [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (shares)		0
Dividend Rate		0.00%
Amount Outstanding		$ 0	374
14,950,000 Depositary Shares each representing a one-fortieth interest in a share of 6.50% Non-Cumulative Preferred Stock, Series H ($1,000 stated value) [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding (shares)		0
Dividend Rate	6.50%	0.00%
Amount Outstanding		$ 0	$ 374