Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 73,953	$ 81,398
Adjustments to reconcile net income to net cash provided by operating activities:
Loss (gain) on disposal of assets	472	(292)
Depreciation	77,018	69,975
Amortization of intangibles	11,849	9,650
Deferred income taxes, net of acquisitions	12,629	23,106
Amortization of debt issuance costs	831	540
Equity-based compensation	10,821	5,962
Interest income on restricted assets	(212)	(245)
Closure and post-closure accretion	1,225	967
Excess tax benefit associated with equity-based compensation	(3,283)	(2,829)
Net change in operating assets and liabilities, net of acquisitions	19,637	1,744
Net cash provided by operating activities	204,940	189,976
Cash flows from investing activities:
Payments for acquisitions, net of cash acquired	(150,222)	(215,962)
Capital expenditures for property and equipment	(67,445)	(46,562)
Proceeds from disposal of assets	1,497	1,862
Decrease (increase) in restricted assets, net of interest income	(577)	2,501
Other	(5,666)	(2,764)
Net cash used in investing activities	(222,413)	(260,925)
Cash flows from financing activities:
Proceeds from long-term debt	334,000	427,500
Principal payments on notes payable and long-term debt	(530,551)	(286,202)
Payment of contingent consideration	(3,849)	(100)
Change in book overdraft	136	(1,918)
Proceeds from option and warrant exercises	851	2,776
Excess tax benefit associated with equity-based compensation	3,283	2,829
Payments for repurchase of common stock	(5,233)	(42,381)
Payments for cash dividends	(21,122)	(17,041)
Tax withholdings related to net share settlements of restricted stock units	(6,010)	(5,271)
Distributions to noncontrolling interests	(94)	(675)
Debt issuance costs	(20)	(1,490)
Proceeds from common stock offering, net	369,584
Net cash provided by financing activities	140,975	78,027
Net increase in cash and equivalents	123,502	7,078
Cash and equivalents at beginning of period	12,643	9,873
Cash and equivalents at end of period	136,145	16,951
Non-cash financing activity:
Liabilities assumed and notes payable issued to sellers of businesses acquired	$ 10,736	$ 107,794