CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Cash flows from operating activities:
Net income	$ 97,274		$ 71,252
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, amortization and impairment	122,953		96,215
Provision for bad debts	1,600
Dry holes and abandonments	56		48
Deferred income tax expense	48,407		38,619
Stock-based compensation expense	5,458		4,307
Net gain on asset disposals	(2,400)	[1]	(1,604)	[1]
Changes in operating assets and liabilities:
Accounts receivable	(38,109)		(48,152)
Income taxes receivable/payable	5,807		2,332
Inventory and other assets	5,332		1,205
Accounts payable	30,418		14,053
Accrued expenses	(12,234)		(5,349)
Other liabilities	(897)		520
Net cash used in operating activities of discontinued operations			(339)
Net cash provided by operating activities	263,665		173,107
Cash flows from investing activities:
Purchase of property and equipment	(263,403)		(182,552)
Proceeds from disposal of assets	4,651		1,954
Net cash provided by investing activities of discontinued operations			25,500
Net cash used in investing activities	(258,752)		(155,098)
Cash flows from financing activities:
Purchase of treasury stock	(15)		(20)
Dividends paid	(7,788)		(7,708)
Tax benefit related to stock-based compensation	166		335
Repayment of other long-term debt	(2,500)		(1,250)
Proceeds from borrowing under revolving credit facility	54,500
Repayment of borrowing under revolving credit facility	(56,000)
Proceeds from exercise of stock options	195		399
Net cash used in financing activities	(11,442)		(8,244)
Effect of foreign exchange rate changes on cash	408		293
Net increase (decrease) in cash and cash equivalents	(6,121)		10,058
Cash and cash equivalents at beginning of period	23,946		27,612
Cash and cash equivalents at end of period	17,825		37,670
Net cash paid during the period for:
Interest, net of capitalized interest of $1,968 in 2012 and $2,043 in 2011	(364)		(1,687)
Income taxes	(1,390)		(179)
Supplemental investing and financing information:
Net increase in payables for purchase of property and equipment	2,553		17,221
Net (increase) decrease in deposits on equipment purchases	$ 1,900		$ (20,503)

[1] Net gains or losses associated with the disposal of assets relate to corporate strategy decisions of the executive management group. Accordingly, the related gains or losses have been separately presented and excluded from the results of specific segments.