Net Income (Loss) Per Share (Tables)

12 Months Ended

Dec. 31, 2016

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

	Year ended December 31,
In thousands except per share amounts	2016		2015			2014
Net income (loss) available to common stockholders	$	55,352	$	(367,183	)	$	(1,186,874	)
Weighted average shares:
Basic	159,853		129,639			102,441
Effect of stock-based compensation plans	3,606		—			—
Diluted	163,459		129,639			102,441
Income (loss) per share:
Basic	$	0.35	$	(2.83	)	$	(11.59	)
Diluted	$	0.34	$	(2.83	)	$	(11.59	)