Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 196,005	$ 159,660	$ 166,171
Adjustments to reconcile net income to net cash provided by operating activities:
Loss on disposal of assets	2,853	1,627	1,657
Depreciation	218,454	169,027	147,036
Amortization of intangibles	25,410	24,557	20,064
Deferred income taxes, net of acquisitions	38,680	29,689	50,989
Amortization of debt issuance costs	3,655	1,993	1,420
Equity-based compensation	15,397	17,289	11,879
Interest income on restricted assets	(386)	(603)	(454)
Interest accretion	4,812	4,000	2,771
Excess tax benefit associated with equity-based compensation	(3,765)	(5,033)	(4,763)
Payment of contingent consideration recorded in earnings	(5,059)
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, net	1,612	1,549	(14,507)
Prepaid expenses and other current assets	1,696	(733)	(4,236)
Accounts payable	(26,993)	2,761	(2,912)
Deferred revenue	1,403	180	4,161
Accrued liabilities	6,117	7,835	9,551
Other long-term liabilities	4,170	2,529	(657)
Net cash provided by operating activities	484,061	416,327	388,170
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for acquisitions, net of cash acquired	(64,156)	(1,579,869)	(257,852)
Proceeds from adjustment to acquisition consideration	18,000
Capital expenditures for property and equipment	(209,874)	(153,517)	(141,924)
Proceeds from disposal of assets	11,019	2,741	4,434
Decrease (increase) in restricted assets, net of interest income	(646)	2,983	351
Other	(5,358)	(6,185)	(5,014)
Net cash used in investing activities	(251,015)	(1,733,847)	(400,005)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from long-term debt	327,600	1,647,000	592,500
Principal payments on notes payable and long-term debt	(493,560)	(609,014)	(421,872)
Payment of contingent consideration recorded at acquisition date	(23,941)	(12,473)	(500)
Change in book overdraft	(110)	398	(227)
Proceeds from option and warrant exercises	2,464	4,057	5,159
Excess tax benefit associated with equity-based compensation	3,765	5,033	4,763
Payments for repurchase of common stock	0	(18,597)	(116,817)
Payments for cash dividends	(51,213)	(44,465)	(35,566)
Tax withholdings related to net share settlements of restricted stock units	(5,439)	(6,062)	(5,511)
Distributions to noncontrolling interests	(198)	(198)	(675)
Debt issuance costs	(2,035)	(7,174)	(6,649)
Proceeds from common stock offering, net		369,584
Net cash provided by (used in) financing activities	(242,667)	1,328,089	14,605
Net increase (decrease) in cash and equivalents	(9,621)	10,569	2,770
Cash and equivalents at beginning of year	23,212	12,643	9,873
Cash and equivalents at end of year	13,591	23,212	12,643
SUPPLEMENTARY DISCLOSURES OF CASH FLOW INFORMATION AND NON-CASH TRANSACTIONS:
Cash paid for income taxes	81,710	69,954	52,729
Cash paid for interest	66,985	49,826	39,499
In connection with its acquisitions, the Company assumed liabilities as follows:
Fair value of assets acquired	67,271	1,748,458	404,550
Cash paid for current year acquisitions	(64,156)	(1,579,869)	(257,852)
Liabilities assumed and notes payable issued to sellers of businesses acquired	$ 3,115	$ 168,589	$ 146,698