Derivative Instruments--Effect of Derivative Instruments on the Consolidated Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Fair value of derivative instruments
Derivative assets, gross	$ 44,715		$ 13,113
Current derivative assets, net	27,797		2,152
Long-term derivative assets, net	16,274		6,403
Derivative liabilities, gross	(917)		(12,792)
Current derivative liabilities, net	(246)		(8,234)
Long-term derivative liabilities, net	(27)		0
Derivative assets (liabilities), net	43,798		321
Current derivative assets (liabilities), net	27,551		(6,082)
Long-term derivative assets (liabilities), net	16,247		6,403
Derivative settlements receivable	1,041		4,616
Derivative settlements payable	75		377
Oil Derivative | Swaps
Fair value of derivative instruments
Derivative assets, gross	5,472		112
Derivative liabilities, gross	0		(2,807)
Derivative assets (liabilities), net	5,472		(2,695)
Oil Derivative | Costless Collars
Fair value of derivative instruments
Derivative assets, gross	2,877		2,776
Derivative liabilities, gross	0		(4)
Derivative assets (liabilities), net	2,877		2,772
Oil Derivative | Enhanced Swaps
Fair value of derivative instruments
Derivative assets, gross	28,745		6,988
Derivative liabilities, gross	(179)		(6,212)
Derivative assets (liabilities), net	28,566		776
Oil Derivative | Purchased Puts
Fair value of derivative instruments
Derivative assets, gross	1,026		74
Derivative liabilities, gross	0		0
Derivative assets (liabilities), net	1,026		74
Natural Gas Derivative | Swaps
Fair value of derivative instruments
Derivative assets, gross	6,595		1,457
Derivative liabilities, gross	(216)		(3,706)
Derivative assets (liabilities), net	6,379		(2,249)
Natural Gas Derivative | Basis Protection Swaps
Fair value of derivative instruments
Derivative assets, gross	0		1,706
Derivative liabilities, gross	(522)		(63)
Derivative assets (liabilities), net	(522)		1,643
Netting adjustments
Fair value of derivative instruments
Derivative assets, gross	(644)	[1]	(4,558)	[1]
Derivative liabilities, gross	644	[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.