CONSOLIDATED CONDENSED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 89,105		$ 96,998
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, amortization and impairment	300,748		273,617
Dry holes and abandonments	321		15
Deferred income tax (benefit) expense	(9,768)		45,748
Stock-based compensation expense	12,959		12,119
Net gain on asset disposals	(4,835)	[1]	(908)	[1]
Changes in operating assets and liabilities:
Accounts receivable	(56,963)		(36,025)
Income taxes receivable/payable	(13,473)		(8,480)
Inventory and other assets	(21,896)		(12,805)
Accounts payable	50,012		25,502
Accrued expenses	12,122		(12,453)
Other liabilities	1,847		15
Net cash provided by operating activities	360,179		383,343
Cash flows from investing activities:
Purchases of property and equipment and acquisitions	(488,038)		(332,598)
Proceeds from disposal of assets	14,991		4,593
Net cash used in investing activities	(473,047)		(328,005)
Cash flows from financing activities:
Purchases of treasury stock	(13,554)		(10,031)
Dividends paid	(29,018)		(14,673)
Tax benefit related to stock-based compensation	8,556		4,862
Repayment of long-term debt	(5,000)		(2,500)
Proceeds from exercise of stock options	22,265		6,959
Net cash used in financing activities	(16,751)		(15,383)
Effect of foreign exchange rate changes on cash	947		(1,801)
Net increase (decrease) in cash and cash equivalents	(128,672)		38,154
Cash and cash equivalents at beginning of period	249,509		110,723
Cash and cash equivalents at end of period	120,837		148,877
Net cash paid during the period for:
Interest, net of capitalized interest of $3,326 in 2014 and $4,358 in 2013	(13,360)		(12,686)
Income taxes	(54,089)		(13,238)
Supplemental non-cash investing and financing information:
Net increase (decrease) in current liabilities for purchases of property and equipment	96,143		(16,169)
Net (increase) decrease in deposits on equipment purchases	$ (25,558)		$ 13,789

[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.