Interim Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Selected Quarterly Financial Information [Abstract]
Revenues	$ 1,178,247	$ 1,179,665	$ 1,243,319	$ 966,837	$ 562,400	$ 537,042	$ 479,893	$ 384,997	$ 4,568,068	$ 1,964,332	$ 1,563,043
Costs and Expenses [Abstract]
Cost of services, rentals and sales	722,814	708,608	711,284	546,767	293,596	285,124	250,667	217,022	2,689,473	1,046,409	848,492
Depreciation, depletion, amortization and accretion	143,009	128,160	135,516	102,596	67,264	61,807	60,020	55,824	509,281	244,915	208,097
Gross Profit	312,424	342,897	396,519	317,474	201,540	190,111	169,206	112,151
Net income from continuing operations	76,275	93,887	142,823	70,157	53,338	54,799	41,375	9,877
Income (loss) from discontinued operations, net of tax			$ (970)	$ (16,237)	$ (33,976)	$ 4,781	$ 6,734	$ 5,626	$ (17,207)	$ (16,835)	$ (4,329)
Earnings Per Share [Abstract]
Continuing operations, basic	$ 0.50	$ 0.60	$ 0.91	$ 0.56	$ 0.67	$ 0.69	$ 0.52	$ 0.12	$ 2.57	$ 2.00	$ 1.09
Continuing operations, diluted	$ 0.50	$ 0.59	$ 0.90	$ 0.55	$ 0.67	$ 0.67	$ 0.51	$ 0.12	$ 2.54	$ 1.97	$ 1.08
Discontinued operations, basic			$ (0.01)	$ (0.13)	$ (0.42)	$ 0.06	$ 0.08	$ 0.07	$ (0.12)	$ (0.21)	$ (0.05)
Discontinued operations, diluted			$ (0.01)	$ (0.13)	$ (0.42)	$ 0.06	$ 0.08	$ 0.07	$ (0.12)	$ (0.21)	$ (0.05)