Asset Retirement Obligations (Details) (USD $)	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012
Asset Retirement Obligation [Abstract]
Beginning asset retirement obligations	$ 197,754,000		$ 136,742,000
Asset Retirement Obligation, Liabilities Incurred	2,468,000		830,000
Changes in estimates	(5,597,000)	[1]	0	[1]
Disposition of wells	(4,079,000)		0
Liabilities settled	(2,849,000)		(5,688,000)
Accretion of discount from continuing operations	3,153,000		2,430,000
Accretion of discount from integrated services	11,000	[2]	0	[2]
Ending asset retirement obligations	190,861,000		134,314,000
Asset retirement obligations, current portions	$ 12,800,000				$ 13,300,000

[1] The change in estimate during the three months ended March 31, 2013 is attributable to lengthening the economic life of certain wells, which reduced the present value of the associated asset retirement obligation.

[2] Accretion of discount from integrated services includes Premier Silica accretion expense, which is recorded as a reduction in third-party income from vertical integration services in interest and other income in the Company's accompanying consolidated statements of operations. See Note K for more information about interest and other income.