Condensed Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 1,655	$ 8,238	[1]
Restricted cash	2,315	11,070	[1]
Accounts receivable, net	64,019	59,923	[1]
Accounts receivable affiliates	9,534	8,518	[1]
Fair value of derivatives	74,778	60,809	[1]
Prepaid expenses and other current assets	7,672	24,492	[1]
Total current assets	159,973	173,050	[1]
Properties and equipment, net	1,329,460	1,301,716	[1]
Assets held for sale	0	148,249	[1]
Fair value of derivatives	36,751	41,175	[1]
Accounts receivable affiliates	2,147	2,836	[1]
Other assets	37,238	30,979	[1]
Total Assets	1,565,569	1,698,005	[1]
Current liabilities:
Accounts payable	56,152	76,027	[1]
Accounts payable affiliates	11,682	10,176	[1]
Production tax liability	19,170	18,949	[1]
Fair value of derivatives	30,513	27,974	[1]
Funds held for distribution	30,093	28,594	[1]
Accrued interest payable	5,069	11,243	[1]
Other accrued expenses	12,583	22,083	[1]
Total current liabilities	165,262	195,046	[1]
Long-term debt	414,809	532,157	[1]
Deferred income taxes	198,082	207,573	[1]
Asset retirement obligations	45,172	46,316	[1]
Fair value of derivatives	25,815	21,106	[1]
Accounts payable affiliates	5,207	6,134	[1]
Other liabilities	29,990	25,561	[1]
Total liabilities	884,337	1,033,893	[1]
Commitments and contingent liabilities			[1]
Shareholders' Equity:
Preferred shares, par value $0.01 per share; authorized 50,000,000 shares; issued: none	0	0	[1]
Common shares, par value $0.01 per share, authorized 100,000,000 shares; issued: 23,659,339 in 2012 and 23,634,958 in 2011	237	236	[1]
Additional paid-in capital	219,139	217,707	[1]
Retained earnings	462,115	446,280	[1]
Treasury shares, at cost: 6,944 in 2012 and 2,938 in 2011	(259)	(111)	[1]
Total shareholders' equity	681,232	664,112	[1]
Total Liabilities and Equity	$ 1,565,569	$ 1,698,005	[1]

[1] Derived from audited 2011 balance sheet.