ADDITIONAL BALANCE SHEET INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
ACCOUNTS RECEIVABLE, NET
Trade Accounts	$ 91,742	$ 111,306
Joint Interest Accounts	3,840	5,417
Other Accounts	778	1,003
Accounts Receivable, Gross	96,360	117,726
Allowance for Doubtful Accounts	(1,240)	(3,345)
Accounts Receivable, Net	95,120	114,381
INVENTORIES
Natural Gas in Storage	3,854	13,513
Tubular Goods and Well Equipment	7,539	7,146
Other	837	619
Inventory, Net	12,230	21,278
OTHER CURRENT ASSETS
Prepaid Balances	1,371	2,290
Restricted Cash	1,907	2,234
Other	88	55
Other Assets Current	3,366	4,579
OTHER ASSETS
Rabbi Trust Deferred Compensation Plan	11,644	10,838
Debt Issuance Costs	16,616	17,680
Other Accounts	1,345	1,342
Other Assets	29,605	29,860
ACCOUNTS PAYABLE
Trade Accounts	14,052	18,253
Natural Gas Purchases	1,966	3,012
Royalty and Other Owners	39,574	48,113
Accrued Capital Costs	136,860	138,122
Taxes Other Than Income	11,847	2,076
Drilling Advances	385	1,489
Wellhead Gas Imbalances	2,351	2,312
Other Accounts	6,153	3,917
Accounts Payable Current	213,188	217,294
ACCRUED LIABILITIES
Employee Benefits	5,858	26,035
Pension and Postretirement Benefits	5,917	6,331
Taxes Other Than Income	11,562	12,297
Interest Payable	14,875	24,701
Derivative Contracts	6,538	385
Other Accounts	1,546	1,169
Accrued Liabilities	46,296	70,918
OTHER LIABILITIES
Rabbi Trust Deferred Compensation Plan	19,183	20,187
Derivative Contracts	1,481
Other Accounts	7,956	11,752
Other Liabilities	$ 28,620	$ 31,939