Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 45,017	$ 52,081
Adjustments to reconcile net income to net cash provided by operating activities:
Loss (gain) on disposal of assets	231	(241)
Depreciation	60,897	57,307
Amortization of intangibles	7,694	6,999
Deferred income taxes, net of acquisitions	17,473	17,753
Amortization of debt issuance costs	670	1,169
Equity-based compensation	5,299	4,821
Interest income on restricted assets	(129)	(117)
Interest accretion	1,465	1,914
Excess tax benefit associated with equity-based compensation	(4,434)	(1,479)
Adjustments to contingent consideration	(75)	808
Payment of contingent consideration recorded in earnings	(33)
Net change in operating assets and liabilities, net of acquisitions	30,641	21,556
Net cash provided by operating activities	164,716	162,571
Cash flows from investing activities:
Payments for acquisitions, net of cash acquired	(3,555)	(90,849)
Capital expenditures for property and equipment	(56,575)	(41,706)
Proceeds from disposal of assets	681	598
Change in restricted assets, net of interest income	260	(1,202)
Other	147	985
Net cash used in investing activities	(59,042)	(132,174)
Cash flows from financing activities:
Proceeds from long-term debt	115,000	263,000
Principal payments on notes payable and long-term debt	(197,024)	(249,624)
Payment of contingent consideration recorded at acquisition date	(2,217)
Change in book overdraft	(151)	25
Excess tax benefit associated with equity-based compensation	4,434	1,479
Payments for repurchase of common stock		(18,366)
Payments for cash dividends	(17,791)	(16,156)
Tax withholdings related to net share settlements of restricted stock units	(9,632)	(6,299)
Distributions to noncontrolling interests	(4)	(43)
Debt issuance costs		(3,032)
Net cash used in financing activities	(107,385)	(29,016)
Net increase (decrease) in cash and equivalents	(1,711)	1,381
Cash and equivalents at beginning of period	10,974	14,353
Cash and equivalents at end of period	9,263	15,734
Non-cash financing activity:
Liabilities assumed and notes payable issued to sellers of businesses acquired	$ 766	$ 7,919