Earnings Per Common Share - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	May 31, 2017
Antidilutive securities excluded from computation of earnings per share
Amount authorized for repurchase					$ 1,500,000,000
Stock repurchased and retired during period (in shares)			4,000
Total consideration for repurchase of common stock			$ 134,000,000
Remaining amount authorized to be repurchased	$ 1,486,000,000		$ 1,486,000,000
Dividends
Cash dividends per common share paid (in dollars per share)	$ 0.1	$ 0.095	$ 0.2	$ 0.19
Cash dividends per common share declared (in dollars per share)	$ 0.1	$ 0.095	$ 0.2	$ 0.19
Stock options
Antidilutive securities excluded from computation of earnings per share
Antidilutive effect on computation of diluted earnings per common share (in shares)	397	380	310	1,000
Long-term stock awards
Antidilutive securities excluded from computation of earnings per share
Stock repurchased And retired during period to offset dilutive impact of awards granted shares (in shares)			800