Earnings Per Common Share (Reconciliation of Earnings (loss) Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements									0	0	0
Basic
Net income (loss)	$ (48,300)	$ (17,540)	$ (77,281)	$ (12,019)	$ (47,573)	$ 12,453	$ (319)	$ (2,579)	$ (155,140)	$ (38,018)	$ (35,932)
Weighted-average shares, outstanding									64,310	63,161	62,213
Income (loss) per common share - Basic	$ (0.75)	$ (0.27)	$ (1.20)	$ (0.19)	$ (0.75)	$ 0.20	$ (0.01)	$ (0.04)	$ (2.41)	$ (0.60)	$ (0.58)
Diluted
Net income (loss)	$ (48,300)	$ (17,540)	$ (77,281)	$ (12,019)	$ (47,573)	$ 12,453	$ (319)	$ (2,579)	$ (155,140)	$ (38,018)	$ (35,932)
Weighted average shares:
Weighted-average shares, outstanding									64,310	63,161	62,213
Weighted-average shares, Diluted									64,310	63,161	62,213
Income (loss) per common share - Diluted	$ (0.75)	$ (0.27)	$ (1.20)	$ (0.19)	$ (0.75)	$ 0.19	$ (0.01)	$ (0.04)	$ (2.41)	$ (0.60)	$ (0.58)