Fair Value Measurements - Carrying Value and Estimated Fair Value of Long-Term Debt (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value of Other Financial Instruments [Line Items]
Senior secured revolving credit facility	$ 93,000	$ 25,000
Total long-term debt	1,360,222	1,293,402
9.875% Senior Notes due 2020
Fair Value of Other Financial Instruments [Line Items]
Senior Notes	294,286	294,031
8.25% Senior Notes due 2021
Fair Value of Other Financial Instruments [Line Items]
Senior Notes	400,000	400,000
7.625% Senior Notes due 2022
Fair Value of Other Financial Instruments [Line Items]
Senior Notes	556,169	556,631
Significant other observable inputs (Level 2) \| Carrying value
Fair Value of Other Financial Instruments [Line Items]
Senior secured revolving credit facility	93,000	25,000
Other secured long-term debt	16,767	17,740
Total long-term debt	1,360,222	1,293,402
Significant other observable inputs (Level 2) \| Carrying value \| 9.875% Senior Notes due 2020
Fair Value of Other Financial Instruments [Line Items]
Senior Notes	294,286	294,031
Significant other observable inputs (Level 2) \| Carrying value \| 8.25% Senior Notes due 2021
Fair Value of Other Financial Instruments [Line Items]
Senior Notes	400,000	400,000
Significant other observable inputs (Level 2) \| Carrying value \| 7.625% Senior Notes due 2022
Fair Value of Other Financial Instruments [Line Items]
Senior Notes	556,169	556,631
Significant other observable inputs (Level 2) \| Estimated fair value
Fair Value of Other Financial Instruments [Line Items]
Senior secured revolving credit facility	93,000	25,000
Other secured long-term debt	16,767	17,740
Total long-term debt	1,429,595	1,392,740
Significant other observable inputs (Level 2) \| Estimated fair value \| 9.875% Senior Notes due 2020
Fair Value of Other Financial Instruments [Line Items]
Senior Notes	342,210	341,250
Significant other observable inputs (Level 2) \| Estimated fair value \| 8.25% Senior Notes due 2021
Fair Value of Other Financial Instruments [Line Items]
Senior Notes	419,680	434,000
Significant other observable inputs (Level 2) \| Estimated fair value \| 7.625% Senior Notes due 2022
Fair Value of Other Financial Instruments [Line Items]
Senior Notes	$ 557,938	$ 574,750

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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