Consolidated statements of cash flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities
Net income	$ 55,687	$ 64,403	$ 42,048
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation, depletion & amortization	192,426	169,307	146,083
Loss on impairment of other assets	3,490	2,000	0
Deferred income taxes	31,734	37,719	35,745
(Gain) loss on hedge reclassification adjustments	(37,134)	(46,746)	27,452
Non-hedge derivative losses (gains)	21,635	(49,685)	(34,408)
Loss on extinguishment of debt	0	21,714	20,592
Net gain on sale of assets	(670)	(149)	(1,284)
Other	2,308	2,864	3,057
Change in assets and liabilities
Accounts receivable	(21,216)	(12,502)	(4,762)
Inventories	(5,923)	(2,304)	328
Prepaid expenses and other assets	811	2,360	1,583
Accounts payable and accrued liabilities	9,977	3,988	16,519
Revenue distribution payable	6,986	(2,648)	3,577
Stock-based compensation	3,942	1,679	3,086
Net cash provided by operating activities	264,053	192,000	259,616
Cash flows from investing activities
Expenditures for property, plant, and equipment	(491,022)	(506,787)	(339,863)
Acquisition of a business	(153,858)	0	0
Proceeds from asset dispositions	111,246	46,246	38,356
Settlement of non-hedge derivative instruments	19,113	37,274	(23,491)
Other	(601)	21	0
Net cash used in investing activities	(515,122)	(423,246)	(324,998)
Cash flows from financing activities
Proceeds from long-term debt	297,797	208,561	21,724
Repayment of long-term debt	(52,100)	(183,482)	(24,785)
Proceeds from Senior Notes	0	556,750	400,000
Repayment of Senior Notes	0	(325,000)	(325,000)
Proceeds from sale and leaseback of assets	24,500	0	0
Principal payments under capital lease obligations	(352)	(10)	(120)
Payment of debt issuance costs and other financing fees	0	(14,516)	(11,858)
Payment of debt extinguishment costs	0	(15,827)	(15,101)
Net cash provided by financing activities	269,845	226,476	44,860
Net increase (decrease) in cash and cash equivalents	18,776	(4,770)	(20,522)
Cash and cash equivalents at beginning of period	29,819	34,589	55,111
Cash and cash equivalents at end of period	$ 48,595	$ 29,819	$ 34,589