Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Condensed Consolidated Statements of Operations [Abstract]
Services	$ 935,560	$ 848,941	$ 2,574,565	$ 2,552,792
Rentals	273,466	247,471	803,431	721,621
Total Revenues	1,209,026	1,096,412	3,377,996	3,274,413
Costs and expenses:
Cost of services (exclusive of items shown separately below)	721,692	671,632	2,023,590	1,969,930
Cost of Services	597,992	581,556	1,704,165	1,706,188
Cost of rentals	123,700	90,076	319,425	263,742
Depreciation, depletion, amortization and accretion	170,154	152,028	493,437	446,432
General and administrative expenses	154,859	147,364	457,631	440,812
Income from operations	162,321	125,388	403,338	417,239
Other income (expense):
Interest expense, net	(24,169)	(25,564)	(72,610)	(81,610)
Gains (Losses) on Extinguishment of Debt				(884)
Other Nonoperating Income (Expense)	(2,051)	(1,697)	(1,480)	41
Income from continuing operations before income taxes	136,101	98,127	329,248	334,786
Income taxes	50,358	30,658	121,822	112,620
Net income (loss) from continuing operations	85,743	67,469	207,426	222,166
Income (loss) from discontinued operations, net of tax	(5,886)	2,366	(15,735)	(20,045)
Net income	$ 79,857	$ 69,835	$ 191,691	$ 202,121
Earnings per share information:
Continuing operations	$ 0.55	$ 0.42	$ 1.33	$ 1.40
Discontinued operations	$ (0.03)	$ 0.02	$ (0.10)	$ (0.13)
Basic earnings per share	$ 0.52	$ 0.44	$ 1.23	$ 1.27
Continuing operations	$ 0.55	$ 0.42	$ 1.31	$ 1.38
Discontinued operations	$ (0.04)	$ 0.01	$ (0.10)	$ (0.12)
Diluted earnings per share	$ 0.51	$ 0.43	$ 1.21	$ 1.26
Common Stock, Dividends, Per Share, Cash Paid	$ 0.08		$ 0.24
Weighted average common shares used in computing earnings per share:
Basic	154,530	159,326	156,424	159,204
Incremental common shares from stock based compensation	1,806	1,557	1,644	1,600
Diluted	156,336	160,883	158,068	160,804