Earnings per Share (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)
Earnings per share
Capped Call, Cap Price | $ / shares	$ 60.00		$ 60.00
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	44	155	59	70
Calculation of basic and diluted earnings per share
Net loss | $	$ (119,907)	$ (168,681)	$ (45,473)	$ (515,891)
Basic weighted-average common shares outstanding	111,277	68,102	111,274	68,090
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0	0	0	0
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities, Treasury Stock Method	0	0	0	0
Diluted weighted-average common shares outstanding	111,277	68,102	111,274	68,090
Basic net income (loss) per common share | $ / shares	$ (1.08)	$ (2.48)	$ (0.41)	$ (7.58)
Diluted net income (loss) per common share | $ / shares	$ (1.08)	$ (2.48)	$ (0.41)	$ (7.58)
Minimum [Member] | Performance Shares [Member]
Earnings per share
Multiplier Applied to PSU Awards at Settlement			0.00
Maximum [Member] | Performance Shares [Member]
Earnings per share
Multiplier Applied to PSU Awards at Settlement			2.00
Convertible Debt [Member] | 1.50% Senior Convertible Notes Due 2021 [Domain]
Earnings per share
Debt Instrument, Face Amount | $	$ 172,500		$ 172,500		$ 172,500
Debt Instrument, Convertible, Conversion Price | $ / shares	$ 40.50		$ 40.50