Basis of Presentation (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Oil and Gas Properties
Discount rate for calculating present value of estimated future net revenues from proved reserves (as a percent)		10.00%
Impairment of oil and gas properties		$ 0
Ceiling limitation used in ceiling test sensitivity analysis		9.00%
Oil, Gas and NGL Sales
Increase in total revenue and processing costs	12,200,000	24,100,000
Portion of residue gas and NGLs yielded by processing (as a percent)		100.00%
Receivables, net of allowance
Trade	95,201,000	95,201,000	83,070,000
Oil and gas sales	333,614,000	333,614,000	265,050,000
Gas gathering, processing, and marketing	20,452,000	20,452,000	19,102,000
Other	189,000	189,000	532,000
Receivables, net	449,456,000	449,456,000	367,754,000
Accounts payable
Trade	84,567,000	84,567,000	80,918,000
Gas gathering, processing, and marketing	41,692,000	41,692,000	35,192,000
Accounts payable	126,259,000	126,259,000	116,110,000
Accrued liabilities
Exploration and development	251,663,000	251,663,000	173,298,000
Taxes other than income	27,134,000	27,134,000	27,509,000
Other	190,155,000	190,155,000	211,688,000
Accrued liabilities	$ 468,952,000	$ 468,952,000	$ 412,495,000