Capital Stock (Details) - USD ($)		12 Months Ended			39 Months Ended
	Jan. 12, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Feb. 02, 2017	Apr. 01, 2014
Class of Stock [Line Items]
Preferred stock dividends paid		$ 0	$ 0	$ 15,000,000
Common stock cash dividends paid		$ 82,000,000	$ 68,000,000	$ 60,000,000
Cash dividends declared per common share (in dollars per share)		$ 0.31	$ 0.25	$ 0.22
Payments for repurchase of common stock		$ 500,000,000	$ 180,000,000	$ 234,000,000	$ 913,000,000
Aggregate common stock repurchased (in shares)					31,214,110
Average cost of aggregate common stock repurchased (in dollars per share)					$ 29.26
Preferred Stock
Class of Stock [Line Items]
Shares converted from preferred to common stock (in shares)							27,573,735
Rate of conversion from preferred to common stock (in shares)							2.7574
Preferred stock dividends paid				15,000,000
Common Stock
Class of Stock [Line Items]
Common stock cash dividends paid		$ 82,000,000	$ 68,000,000	$ 60,000,000
Common stock repurchased (in shares)		16,706,392
Average cost of common stock repurchased (in dollars per share)		$ 29.93
Payments for repurchase of common stock		$ 500,000,000
Subsequent Event | Common Stock
Class of Stock [Line Items]
Cash dividends declared per common share (in dollars per share)	$ 0.1
Dividends declared on common stock	$ 25,000,000
Stock repurchase program, authorized amount						$ 2,100,000,000.0
Payments for Share Repurchases Related to Employee Stock Based Compensation | Common Stock
Class of Stock [Line Items]
Common stock repurchased (in shares)		0