Earnings Per Common Share - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	Oct. 24, 2017	Aug. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	May 31, 2017
Antidilutive securities excluded from computation of earnings per share
Amount authorized for repurchase		$ 150,000,000					$ 1,500,000,000
Stock repurchased and retired during period (in shares)					8,000
Total consideration for repurchase of common stock					$ 312,000,000
Stock repurchased during period (in shares)		3,300
Remaining amount authorized to be repurchased			$ 1,300,000,000		$ 1,300,000,000
Dividends
Cash dividends per common share paid (in dollars per share)			$ 0.1	$ 0.095	$ 0.3	$ 0.285
Cash dividends per common share declared (in dollars per share)			$ 0.105	$ 0.1	$ 0.305	$ 0.29
Stock options
Antidilutive securities excluded from computation of earnings per share
Antidilutive effect on computation of diluted earnings per common share (in shares)			397	0	339	609
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
Forecast
Antidilutive securities excluded from computation of earnings per share
Stock repurchased during period (in shares)	700