Summary of Significant Accounting Policies Earnings Per Share (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Capped call, cap price | $ / shares	$ 60.00
Anti-dilutive Securities Excluded from Computation of Earnings Per Share, Amount	264	280	256
Earnings Per Share Reconciliation [Abstract]
Net loss | $	$ (160,843)	$ (757,744)	$ (447,710)
Basic weighted-average common shares outstanding	111,428	76,568	67,723
Dilutive effect of non-vested RSUs and contingent PSUs	0	0	0
Dilutive effect of Senior Convertible Notes	0	0	0
Diluted weighted-average common shares outstanding	111,428	76,568	67,723
Basic net loss per common share | $ / shares	$ (1.44)	$ (9.90)	$ (6.61)
Diluted net loss per common share | $ / shares	$ (1.44)	$ (9.90)	$ (6.61)
Performance Shares [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Award Vesting Period	3 years
Multiplier Applied to PSU Awards at Settlement		0.2	1.0
Minimum [Member] | Performance Shares [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Multiplier Applied to PSU Awards at Settlement	0
Maximum [Member] | Performance Shares [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Multiplier Applied to PSU Awards at Settlement	2
1.50% Senior Convertible Notes Due 2021 [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Senior Notes, face amount | $	$ 172,500	$ 172,500
Senior Convertible Notes, conversion price | $ / shares	$ 40.50