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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 |  |

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