Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
OPERATING ACTIVITIES:
Net income	$ 111,305	$ 99,213
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, and amortization	190,813	159,369
(Gain) loss on derivatives	29,075	(13,429)
Cash (payments) receipts on derivatives settled	(17,955)	3,868
Deferred tax expense	52,000	57,817
Gain on disposition of assets	(9,621)	(3,399)
Employee stock compensation plans	11,655	10,654
Other, net	3,076	3,005
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts receivable	(45,150)	(13,001)
Accounts payable	(11,585)	2,219
Material and supplies	2,458	(751)
Accrued liabilities	7,440	11,313
Other, net	2,017	1,010
Net cash provided by operating activities	325,528	317,888
INVESTING ACTIVITIES:
Capital expenditures	(420,235)	(339,300)
Proceeds from disposition of assets	40,825	16,829
Other	303	0
Net cash used in investing activities	(379,107)	(322,471)
FINANCING ACTIVITIES:
Borrowings under credit agreement	129,300	183,900
Payments under credit agreement	(129,300)	(185,000)
Net payments on capitalized leases	(711)	0
Proceeds from exercise of stock options	887	81
Book overdrafts	35,888	5,669
Net cash provided by financing activities	36,064	4,650
Net increase (decrease) in cash and cash equivalents	(17,515)	67
Cash and cash equivalents, beginning of period	18,593	974
Cash and cash equivalents, end of period	1,078	1,041
Cash paid during the year for: [Abstract]
Interest paid (net of capitalized)	6,223	6,273
Income taxes	15,800	7,100
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	(29,247)	28,615
Non-cash additions to oil and natural gas properties related to asset retirement obligations	(15,432)	(11,945)
Non-cash additions to property, plant, and equipment acquired under capital leases	$ (26,510)	$ 0