Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 41,680	$ 31,439
Adjustments to reconcile net income to net cash provided by operating activities:
Loss (gain) on disposal of assets	(322)	715
Depreciation	51,649	37,173
Amortization of intangibles	6,438	5,631
Deferred income taxes, net of acquisitions	16,524	12,101
Amortization of debt issuance costs	858	415
Equity-based compensation	3,594	7,596
Interest income on restricted assets	(113)	(112)
Interest accretion	1,293	836
Excess tax benefit associated with equity-based compensation	(2,098)	(3,005)
Net change in operating assets and liabilities, net of acquisitions	13,455	7,792
Net cash provided by operating activities	132,958	100,581
Cash flows from investing activities:
Payments for acquisitions, net of cash acquired		(138,908)
Proceeds from adjustment to acquisition consideration	18,000
Capital expenditures for property and equipment	(36,905)	(27,953)
Proceeds from disposal of assets	723	753
Other	(926)	(1,861)
Net cash used in investing activities	(19,108)	(167,969)
Cash flows from financing activities:
Proceeds from long-term debt	26,500	184,000
Principal payments on notes payable and long-term debt	(134,083)	(474,865)
Payment of contingent consideration	(229)	(3,528)
Change in book overdraft	(17)	321
Proceeds from option and warrant exercises	761	530
Excess tax benefit associated with equity-based compensation	2,098	3,005
Payments for cash dividends	(12,310)	(10,010)
Tax withholdings related to net share settlements of restricted stock units	(5,280)	(5,904)
Distributions to noncontrolling interests	(198)	(95)
Debt issuance costs	(24)
Proceeds from common stock offering, net		369,460
Net cash provided by (used in) financing activities	(122,782)	62,914
Net decrease in cash and equivalents	(8,932)	(4,474)
Cash and equivalents at beginning of period	23,212	12,643
Cash and equivalents at end of period	14,280	8,169
Non-cash financing activity:
Liabilities assumed and notes payable issued to sellers of businesses acquired		$ 9,974