Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities
Net income	$ 17,829	$ 42,698	$ 20,268	$ 78,890
Adjustments to reconcile net income to net cash provided by operating activities:
Depletion, depreciation and amortization	14,862	15,660	29,534	31,723
Loss/(Gain) on disposal of property, plant and equipment	297	(207)	292	(226)
Abandonment of non-producing property	0	0	2,835	0
Accretion of asset retirement obligation	157	145	310	286
Amortization of debt issuance costs	315	246	629	491
Share based compensation and other benefits	4,115	2,689	7,887	5,789
Changes in operating assets and liabilities:
Inventories	11,486	(15,505)	9,920	(55,569)
Trade receivables	802	81	(2,380)	(393)
Accrued compensation and benefits	377	3,051	1,234	4,341
Accounts payable	(7,029)	1,450	(2,336)	4,644
Property, production and franchise taxes payable	(22)	1,273	396	2,944
Income taxes payable	(268)	5,737	(3,115)	9,821
Workers compensation	502	(78)	502	(554)
Restricted cash	0	0	75	3,000
Other	(4,051)	1,571	(10,683)	7,496
Net cash provided by operating activities	39,372	58,811	55,368	92,683
Cash flows from investing activities
Capital expenditures	(36,593)	(23,110)	(59,313)	(46,295)
Purchase of long-term investment	0	0	0	(616)
Proceeds from disposal of property, plant and equipment	20	207	28	228
Purchases of investments	(26,637)	(32,801)	(31,887)	(98,096)
Proceeds from maturities of investments	19,088	58,575	23,549	137,017
Net cash (used in) provided by investing activities	(44,122)	2,871	(67,623)	(7,762)
Cash flows from financing activities
Proceeds from sale of noncontrolling interest, net of transaction costs	94,669	0	93,821	0
Issuance of long-term debt	7,176	0	7,176	0
Payments on long term debt and capital lease obligations	(495)	0	(495)	0
Payments for debt issuance costs	0	0	(219)	0
Issuance of common stock	3	7	32	725
Net cash provided by financing activities	101,353	7	100,315	725
Cash and cash equivalents
Net increase	96,603	61,689	88,060	85,646
Balance at beginning of period	100,554	43,320	109,097	19,363
Balance at end of period	$ 197,157	$ 105,009	$ 197,157	$ 105,009