ADDITIONAL BALANCE SHEET INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
ACCOUNTS RECEIVABLE, NET
Trade Accounts	$ 82,915	$ 111,306
Joint Interest Accounts	3,703	5,417
Other Accounts	3,561	1,003
Accounts Receivable, Gross	90,179	117,726
Allowance for Doubtful Accounts	(1,012)	(3,345)
Accounts Receivable, Net	89,167	114,381
INVENTORIES
Natural Gas in Storage	5,466	13,513
Tubular Goods and Well Equipment	6,247	7,146
Other Accounts	272	619
Inventory, Net	11,985	21,278
OTHER CURRENT ASSETS
Prepaid Balances and Other	4,821	2,345
Restricted Cash	1,907	2,234
Other Assets Current	6,728	4,579
OTHER ASSETS
Rabbi Trust Deferred Compensation Plan	11,146	10,838
Debt Issuance Costs	19,351	17,680
Equity Method Investment	2,078
Other Accounts	1,317	1,342
Other Assets	33,892	29,860
ACCOUNTS PAYABLE
Trade Accounts	25,406	18,253
Natural Gas Purchases	3,062	3,012
Royalty and Other Owners	47,094	48,113
Accrued Capital Costs	153,061	138,122
Taxes Other Than Income	791	2,076
Drilling Advances	344	1,489
Wellhead Gas Imbalances	2,375	2,312
Other Accounts	5,284	3,917
Accounts Payable Current	237,417	217,294
ACCRUED LIABILITIES
Employee Benefits	11,375	26,035
Pension and Postretirement Benefits	4,838	6,331
Taxes Other Than Income	12,647	12,297
Interest Payable	23,557	24,701
Derivative Contracts	193	385
Other Accounts	1,506	1,169
Accrued Liabilities	54,116	70,918
OTHER LIABILITIES
Rabbi Trust Deferred Compensation Plan	20,883	20,187
Derivative Contracts	951
Other Accounts	12,716	11,752
Other Liabilities	$ 34,550	$ 31,939