Earnings Per Share - Computations of Basic and Diluted EPS (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Basic:
Net income (loss)	$ (10,671)	$ (2,635)	$ (38,494)	$ 17,007
Less undistributed earnings allocated to participating securities	0	0	0	(96)
Undistributed earnings (loss) allocated to common shares	$ (10,671)	$ (2,635)	$ (38,494)	$ 16,911
Weighted average number of shares outstanding, basic	107,767	105,357	106,838	105,324
Diluted:
Undistributed earnings (loss) allocated to common shares	$ (10,671)	$ (2,635)	$ (38,494)	$ 16,911
Share-based awards other than participating securities	$ 0	$ 0	$ 0	$ 0
Share-based awards other than participating securities (in shares)	0	0	0	0
Undistributed earnings reallocated to participating securities	$ 0	$ 0	$ 0	$ 0
Net income (loss)	$ (10,671)	$ (2,635)	$ (38,494)	$ 16,911
Weighted average number of shares outstanding, diluted	107,767	105,357	106,838	105,324