Fair Value Measurements (Details 2) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2011	Dec. 31, 2013 A		Dec. 31, 2012		Dec. 31, 2011
Proved Oil and Gas Properties
Discount rate used for fair value of oil and gas properties (as a percent)		12.00%
Net Profit Plan liability [Member]
Liability measured at fair value using Level 3 inputs
Discount rate to calculate liability pools currently in payout (as a percent)		12.00%
Number of periods used for price assumptions of strip prices of liabilities		5
Period used for price assumptions of strip prices of liabilities (in years)		1
Percentage change in commodity prices (as a percent)		5.00%
Change in liability due to change in commodity prices by 5 percent		$ 5,000,000
Percentage increase in discount rate (as a percent)		1.00%
Increase in liability due to a 1 percent decrease in discount rate		2,000,000
Decrease in liability due to a 1 percent increase in discount rate		2,000,000
Liability measured at fair value using Level 3 inputs
Net Profits Plan Liability: Beginning Balance	135,850,000	78,827,000		107,731,000		135,850,000
Net increase (decrease) in liability		3,527,000	[1]	(9,251,000)	[1]	2,269,000	[1]
Net settlements		(25,369,000)	[1],[2],[3]	(19,653,000)	[1],[2],[3]	(30,388,000)	[1],[2],[3]
Transfers in (out) of Level 3		0		0		0
Net Profits Plan Liability: Ending balance		56,985,000		78,827,000		107,731,000
Amount paid for settlement of liabilities	2,600,000
Net Profits Plan [Member]
Liability measured at fair value using Level 3 inputs
Amount of cash payments related to divested properties		10,300,000		2,300,000		6,300,000
6.625% Senior Notes Due 2019 [Member]
Liability measured at fair value using Level 3 inputs
Long-term Debt, Fair Value		374,290,000		371,875,000
6.50% Senior Notes Due 2021 [Member]
Liability measured at fair value using Level 3 inputs
Long-term Debt, Fair Value		373,625,000		371,070,000
6.50% Senior Notes Due 2023 [Member]
Liability measured at fair value using Level 3 inputs
Long-term Debt, Fair Value		422,000,000		424,200,000
5% Senior Notes Due 2024 [Member]
Liability measured at fair value using Level 3 inputs
Long-term Debt, Fair Value		$ 475,315,000	[4]	$ 0	[4]

[1] Net changes in the Net Profits Plan liability are shown in the Change in Net Profits Plan liability line item of the accompanying statements of operations.

[2] During 2011, the Company elected to cash out several Net Profits Plan pools with a $2.6 million direct payment. As a result, the Company reduced its Net Profits Plan liability by that amount. There was no impact on the accompanying statements of operations for the period ended December 31, 2011, related to these settlements.

[3] Settlements represent cash payments made or accrued under the Net Profits Plan. The amounts in the table include cash payments made or accrued under the Net Profits Plan of $10.3 million, $2.3 million, and $6.3 million relating to divestiture proceeds for the years ended December 31, 2013, 2012, and 2011, respectively.

[4] (1) The 2024 Notes were issued on May 20, 2013.