Fair Value Measurements Long-term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2017		Dec. 31, 2016
6.50% Senior Notes Due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	6.50%
Senior Notes, face amount	$ 344,611	[1]	$ 346,955	[2]
6.125% Senior Notes Due 2022 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	6.125%
Senior Notes, face amount	$ 561,796		561,796	[2]
6.50% Senior Notes Due 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	6.50%
Senior Notes, face amount	$ 394,985		394,985	[2]
5% Senior Notes Due 2024 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	5.00%
Senior Notes, face amount	$ 500,000		500,000
5.625% Senior Notes Due 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	5.625%
Senior Notes, face amount	$ 500,000		500,000
6.75% Senior Notes Due 2026 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	6.75%
Senior Notes, face amount	$ 500,000		500,000	[3]
1.50% Senior Convertible Notes Due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	1.50%
Senior Notes, face amount	$ 172,500		172,500
Senior Notes [Member] | 6.50% Senior Notes Due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	6.50%
Senior Notes, face amount	$ 344,611
Long-term Debt, Fair Value	$ 349,780		354,546
Senior Notes [Member] | 6.125% Senior Notes Due 2022 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	6.125%
Senior Notes, face amount	$ 561,796
Long-term Debt, Fair Value	$ 565,830		570,925
Senior Notes [Member] | 6.50% Senior Notes Due 2023 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	6.50%
Senior Notes, face amount	$ 394,985
Long-term Debt, Fair Value	$ 397,947		403,134
Senior Notes [Member] | 5% Senior Notes Due 2024 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	5.00%
Senior Notes, face amount	$ 500,000
Long-term Debt, Fair Value	$ 471,660		475,975
Senior Notes [Member] | 5.625% Senior Notes Due 2025 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	5.625%
Senior Notes, face amount	$ 500,000
Long-term Debt, Fair Value	$ 477,350		485,000
Senior Notes [Member] | 6.75% Senior Notes Due 2026 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	6.75%
Senior Notes, face amount	$ 500,000
Long-term Debt, Fair Value	$ 502,500		516,565
Convertible Debt [Member] | 1.50% Senior Convertible Notes Due 2021 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior Notes, interest rate, stated percentage	1.50%
Senior Notes, face amount	$ 172,500		172,500
Long-term Debt, Fair Value	$ 163,240		$ 202,189

[1] During the first quarter of 2017, the Company repurchased a total of $2.3 million in aggregate principal amount of 6.50% Senior Notes due 2021 in open market transactions at a slight premium. The Company canceled all of these repurchased Senior Notes upon cash settlement.

[2] During the first quarter of 2016, the Company repurchased a total of $46.3 million in aggregate principal amount of certain of its Senior Notes in open market transactions for a settlement amount of $29.9 million, excluding interest. The Company recorded a net gain on extinguishment of debt of approximately $15.7 million for the nine months ended September 30, 2016. This amount includes a gain of approximately $16.4 million associated with the discount realized upon repurchase, which was partially offset by approximately $0.7 million related to the acceleration of unamortized deferred financing costs. The Company canceled all of these repurchased Senior Notes upon cash settlement.

[3] On September 12, 2016, the Company issued 6.75% Senior Notes due September 15, 2026. The Company received net proceeds of $491.6 million after deducting paid and accrued fees. The net proceeds were used to partially fund the Rock Oil Acquisition that closed on October 4, 2016.