Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
OPERATING ACTIVITIES:
Net income	$ 52,439	$ 41,027
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	79,047	61,577
Unrealized loss on derivatives	1,993	2,328
Deferred tax expense	33,105	25,414
(Gain) loss on disposition of assets	(588)	170
Stock compensation plans	3,692	3,286
Other	1,188	895
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts receivable	(2,860)	(4,716)
Accounts payable	(21,735)	(15,952)
Material and supplies inventory	417	26
Accrued liabilities	1,545	101
Contract advances	4	2,665
Other - net	(300)	4,384
Net cash provided by operating activities	147,947	121,205
INVESTING ACTIVITIES:
Capital expenditures	(192,824)	(165,617)
Producing property and other acquisitions	(46)	(4,052)
Proceeds from disposition of assets	3,451	457
Net cash used in investing activities	(189,419)	(169,212)
FINANCING ACTIVITIES:
Borrowings under line of credit	103,700	88,800
Payments under line of credit	(87,900)	(66,800)
Proceeds from exercise of stock options	0	513
Book overdrafts	26,032	25,371
Net cash provided by financing activities	41,832	47,884
Net increase (decrease) in cash and cash equivalents	360	(123)
Cash and cash equivalents, beginning of period	835	1,359
Cash and cash equivalents, end of period	$ 1,195	$ 1,236

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Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits are not generally reported as cash and cash equivalents. Includes cash and cash equivalents associated with the entity's continuing operations. Excludes cash and cash equivalents associated with the disposal group (and discontinued operation).