CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (UNAUDITED) - 6 months ended Jun. 30, 2016 - USD ($) shares in Millions, $ in Millions	Total	Common Stock		Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive (Loss) Income	[2]
Balance (in shares) at Dec. 31, 2015		92	[1]			20
Balance at Dec. 31, 2015	$ 1,476	$ 1		$ 2,197	$ 1,088	$ (1,560)	$ (250)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	226				226
Foreign currency translation adjustments	60						60
Fixed price diesel swaps	3						3
Stock compensation expense, net				22
Shares repurchased and retired				(11)
Repurchase of common stock (in shares)		(5)	[1]			5
Repurchase of common stock						$ (325)
Excess tax benefits from share-based payment arrangements, net				51
Balance (in shares) at Jun. 30, 2016		87	[1]			25
Balance at Jun. 30, 2016	$ 1,502	$ 1		$ 2,259	$ 1,314	$ (1,885)	$ (187)

[1] Common stock outstanding decreased by approximately 6 million net shares during the year ended December 31, 2015.

[2] The Accumulated Other Comprehensive Loss balance primarily reflects foreign currency translation adjustments.