Earnings Per Common Share (Details 2) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	1 Months Ended		3 Months Ended			9 Months Ended
	Sep. 30, 2015	Aug. 31, 2015	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive securities excluded from computation of earnings per share
Repurchase and retirement of common stock (in shares)						15,500
Total consideration for repurchase of common stock including unpaid cash						$ 407
Stock repurchased during period		$ 200
Stock repurchased during period (in shares)	1,500	6,100
Remaining number of shares authorized to be repurchased	29,500		29,500			29,500
Dividends
Cash dividends per common share paid (in dollars per share)			$ 0.090		$ 0.090	$ 0.270	$ 0.240
Cash dividends per common share declared (in dollars per share)			$ 0.095		$ 0.090	$ 0.275	$ 0.255
Stock Options
Antidilutive securities excluded from computation of earnings per share
Antidilutive effect on computation of diluted earnings per common share (in shares)			4,000		8,000	6,000	8,000
Long-term stock awards
Antidilutive securities excluded from computation of earnings per share
Repurchase and retirement of common stock to offset the dilutive impact of stock awards (in shares)				720