Earnings Per Share (Details) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Aug. 12, 2016 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Capped Call, Cap Price | $ / shares					$ 60.00
Anti-dilutive shares excluded from earnings per share | shares		684	0	264
Earnings Per Share Reconciliation [Abstract]
Net income (loss) | $		$ (187,001)	$ 508,407	$ (160,843)
Basic weighted-average common shares outstanding | shares		112,544	111,912	111,428
Dilutive effect of non-vested RSUs and contingent PSUs | shares		0	1,590	0
Diluted weighted-average common shares outstanding | shares		112,544	113,502	111,428
Basic net income (loss) per common share | $ / shares		$ (1.66)	$ 4.54	$ (1.44)
Diluted net income (loss) per common share | $ / shares		$ (1.66)	$ 4.48	$ (1.44)
1.50% Senior Convertible Notes Due 2021 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Senior Convertible Notes, principal amount | $	$ 172,500	$ 172,500	$ 172,500		$ 172,500
Senior Convertible Notes, conversion price | $ / shares	$ 40.50	$ 40.50
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Multiplier applied to PSU awards at settlement	0	0	0	0
Minimum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier applied to PSU awards at settlement	0	0
Maximum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier applied to PSU awards at settlement	2	2