Consolidated statements of cash flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 1,409	$ 26,235
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income tax expense	1,263	14,757
Depreciation, depletion and amortization	65,130	51,523
Non-cash stock-based compensation	3,217	2,247
Accretion of asset retirement obligations	394	264
Unrealized (gain) loss on derivative financial instruments, net	20,536	3,334
Premiums paid for derivative financial instruments	(2,422)	(1,332)
Amortization of premiums paid for derivative financial instruments	151	150
Amortization of deferred loan costs	1,294	1,060
Other	16	(45)
(Increase) decrease in accounts receivable	(5,602)	(14,801)
(Increase) decrease in other current assets	(2,574)	(6,203)
Increase (decrease) in accounts payable	(18,523)	27,918
Increase (decrease) in undistributed revenues and royalties	3,524	3,907
Increase (decrease) in accrued compensation and benefits	(4,221)	(5,698)
Increase (decrease) in other accrued liabilities	(792)	(12,319)
Increase (decrease) in other noncurrent liabilities	162	(51)
Increase (decrease) in fair value of performance unit awards	98	456
Net cash provided by operating activities	63,060	91,402
Capital expenditures:
Investment in equity method investee	(938)	0
Oil and natural gas properties	(187,813)	(247,280)
Pipeline and gas gathering assets	(4,046)	(3,859)
Other fixed assets	(6,588)	(1,053)
Net cash used in investing activities	(199,385)	(252,192)
Cash flows from financing activities:
Borrowings on revolving credit facilities	135,000	145,000
Purchase of treasury stock	(875)	0
Net cash provided by financing activities	134,125	145,000
Net decrease in cash and cash equivalents	(2,200)	(15,790)
Cash and cash equivalents, beginning of period	33,224	28,002
Cash and cash equivalents, end of period	31,024	12,212
Cash paid during the period:
Interest, net of $95 and 379, respectively, of capitalized interest for the nine months ended September 30, 2012 and 2011, respectively	$ 27,649	$ 26,726