Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2015

Stockholders' Equity Note [Abstract]

Common Stock Rollforward

The following summarizes the changes in the Company’s outstanding shares of common stock:

millions	2015	2014	2013
Shares of common stock issued
Shares at January 1	526	523	519
Exercise of stock options	1	2	2
Issuance of restricted stock	1	1	2
Shares at December 31	528	526	523
Shares of common stock held in treasury
Shares at January 1	19	19	18
Shares received for restricted stock vested and options exercised	1	—	1
Shares at December 31	20	19	19
Shares of common stock outstanding at December 31	508	507	504

Earnings Per Share Table

The following provides a reconciliation between basic and diluted EPS attributable to common stockholders for the years ended December 31:

millions except per-share amounts	2015			2014			2013
Net income (loss)
Net income (loss) attributable to common stockholders	$	(6,692	)	$	(1,750	)	$	801
Less distributions on participating securities	3			4			2
Less undistributed income allocated to participating securities	—			—			4
Basic	$	(6,695	)	$	(1,754	)	$	795
Diluted	$	(6,695	)	$	(1,754	)	$	795
Shares
Average number of common shares outstanding—basic	508			506			502
Dilutive effect of stock options	—			—			3
Average number of common shares outstanding—diluted	508			506			505
Excluded due to anti-dilutive effect	11			11			4
Net income (loss) per common share
Basic	$	(13.18	)	$	(3.47	)	$	1.58
Diluted	$	(13.18	)	$	(3.47	)	$	1.58