Derivative Instruments--Effect of Derivative Instruments on the Consolidated Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative assets, gross	$ 3,100		$ 13,113
Current derivative assets, net	0		2,152
Long-term derivative assets, net	2,847		6,403
Derivative liabilities, gross	(23,223)		(12,792)
Current derivative liabilities, net	(22,830)		(8,234)
Long-term derivative liabilities, net	(140)		0
Derivative assets (liabilities), net	(20,123)		321
Current derivative assets (liabilities), net	(22,830)		(6,082)
Long-term derivative assets (liabilities), net	2,707		6,403
Derivative settlements receivable	156		4,616
Derivative settlements payable	5,339		377
Oil Derivative | Swaps
Derivatives, Fair Value [Line Items]
Derivative assets, gross	0		112
Derivative liabilities, gross	(3,345)		(2,807)
Derivative assets (liabilities), net	(3,345)		(2,695)
Oil Derivative | Costless Collars
Derivatives, Fair Value [Line Items]
Derivative assets, gross	733		2,776
Derivative liabilities, gross	(824)		(4)
Derivative assets (liabilities), net	(91)		2,772
Oil Derivative | Enhanced Swaps
Derivatives, Fair Value [Line Items]
Derivative assets, gross	1,621		6,988
Derivative liabilities, gross	(11,308)		(6,212)
Derivative assets (liabilities), net	(9,687)		776
Oil Derivative | Put Options Purchased
Derivatives, Fair Value [Line Items]
Derivative assets, gross	10		74
Derivative liabilities, gross	0		0
Derivative assets (liabilities), net	10		74
Natural Gas Derivative | Swaps
Derivatives, Fair Value [Line Items]
Derivative assets, gross	665		1,457
Derivative liabilities, gross	(7,457)		(3,706)
Derivative assets (liabilities), net	(6,792)		(2,249)
Natural Gas Derivative | Basis Protection Swaps
Derivatives, Fair Value [Line Items]
Derivative assets, gross	71		1,706
Derivative liabilities, gross	(289)		(63)
Derivative assets (liabilities), net	(218)		1,643
Netting adjustments
Derivatives, Fair Value [Line Items]
Derivative assets, gross	(253)	[1]	(4,558)	[1]
Derivative liabilities, gross	253	[1]	4,558	[1]
Derivative assets (liabilities), net	$ 0	[1]	$ 0	[1]

[1] Amounts represent the impact of master netting agreements that allow us to net settle positive and negative positions with the same counterparty. Positive and negative positions with a counterparty are netted only to the extent that they relate to the same current versus noncurrent classification on the balance sheet.