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Long-Term Debt - Additional Information (Detail) (USD $)
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1 Months Ended | 12 Months Ended | 1 Months Ended | 12 Months Ended | 1 Months Ended | 12 Months Ended | ||||||||||
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Oct. 12, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Oct. 24, 2012
8.50% Senior Notes, due June 2019
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Jun. 10, 2011
8.50% Senior Notes, due June 2019
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Dec. 31, 2012
8.50% Senior Notes, due June 2019
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Dec. 31, 2011
8.50% Senior Notes, due June 2019
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Dec. 31, 2012
8.25% Senior Notes Due June 2014
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Nov. 30, 2012
Revolving Bank Credit Facility Due May 2015
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Dec. 31, 2012
Revolving Bank Credit Facility Due May 2015
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Dec. 31, 2011
Revolving Bank Credit Facility Due May 2015
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May 05, 2011
Revolving Bank Credit Facility Due May 2015
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| Debt Instrument [Line Items] | ||||||||||||||||
| Long-term Debt unsecured | $ 300,000,000 | $ 600,000,000 | $ 900,000,000 | $ 600,000,000 | ||||||||||||
| Debt issuance, premium percentage | 106.00% | |||||||||||||||
| Senior notes interest rate | 8.50% | 8.50% | 8.50% | 8.50% | 8.25% | |||||||||||
| Senior notes maturity date | Jun. 15, 2019 | Jun. 15, 2019 | Jun. 15, 2019 | Jun. 15, 2019 | Jun. 01, 2014 | May 01, 2015 | May 01, 2015 | |||||||||
| Net proceeds after fees and expenses | 312,000,000 | 593,500,000 | ||||||||||||||
| Annual effective interest rate | 7.73% | 8.60% | 5.00% | |||||||||||||
| Senior notes | 1,087,611,000 | [1] | 717,000,000 | [1] | 450,000,000 | |||||||||||
| Cost related to repurchase of senior notes | 22,000,000 | |||||||||||||||
| Senior notes payment terms | Semi-annually in arrears on June 15 and December 15 of each year | |||||||||||||||
| Estimated senior notes fair value | 963,000,000 | 612,000,000 | ||||||||||||||
| Revolving bank credit facility borrowing base | 600,000,000 | 525,000,000 | ||||||||||||||
| Increase to borrowing base | 725,000,000 | |||||||||||||||
| Credit agreement expiration date | May 05, 2015 | |||||||||||||||
| Restriction on payment of dividends | 60,000,000 | |||||||||||||||
| Common stock and senior note repurchases | 100,000,000 | |||||||||||||||
| One-time waiver requested and granted for cash dividends | 85,000,000 | |||||||||||||||
| Maximum letter of credit issued | 90,000,000 | |||||||||||||||
| Revolving bank credit facility interest rate description | Issuance of additional Senior Notes above the $600.0 million level and provided for a reduction in the borrowing base of 25% of every $1.00 of Senior Notes above $600.0 million until such time as the borrowing base is re-determined. | Borrowings under the revolving bank credit facility bear interest at the applicable LIBOR plus a margin that varies from 2.00% to 2.75% depending on the level of total borrowings under the Credit Agreement, or an alternative base rate equal to the applicable margin ranging from 1.00% to 1.75% plus the highest of the (a) Prime Rate, (b) Federal Funds Rate plus 0.50%, and (c) LIBOR plus 1.0%. | ||||||||||||||
| Unused portion of the borrowing base commitment fee | 0.50% | |||||||||||||||
| Line of credit facility conditional potential additional borrowing capacity | 1.00 | |||||||||||||||
| Percentage of base of senior notes for potential additional borrowing capacity | 25.00% | |||||||||||||||
| Unamortized debt issuance cost written off | 700,000 | |||||||||||||||
| Revolving bank credit facility borrowings outstanding | 170,000,000 | 117,000,000 | ||||||||||||||
| Letters of credit outstanding | $ 600,000 | $ 400,000 | ||||||||||||||
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