Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 93,927	$ 72,035	$ 12,344
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	78,666	77,447	72,808
Loss on extinguishment of debt	0	0	63,682
Amortization of original issue discount and deferred financing costs	3,583	3,052	2,763
Interest paid in kind	0	0	2,143
Non-cash revenue and other	191	(149)	(618)
Impairment losses on long-lived assets	41	206	765
Loss on disposal of fixed assets	351	667	566
Stock-based compensation	9,200	7,922	10,692
Deferred income taxes	(758)	(13,376)	(13,410)
Deferred rent	2,736	3,092	2,985
Changes in assets and liabilities:
Accounts receivable	(13,340)	(4,604)	(11,458)
Prepaid expenses and other current assets	3,825	2,174	(5,393)
Income taxes	(12,073)	3,505	(13,386)
Accounts payable and accrued expenses	(6,448)	9,589	365
Deferred revenue	2,955	14,259	22,350
Accrued rent and related obligations	4,642	3,222	2,180
Other assets	(14,296)	(1,672)	149
Other current and long-term liabilities	16,854	(3,072)	10,152
Net cash provided by operating activities	170,056	174,297	159,679
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of fixed assets	(77,785)	(66,194)	(69,509)
Proceeds from the disposal of fixed assets	50	385	189
Purchase of long-term investments	0	0	(2,000)
Settlement of purchase price for prior year acquisitions	23	1,030	0
Payments for acquisitions—net of cash acquired	(77,642)	(13,222)	(129,812)
Net cash used in investing activities	(155,354)	(78,001)	(201,132)
CASH FLOWS FROM FINANCING ACTIVITIES:
Borrowings of long-term debt, net of issuance costs of $3.2 million in 2014 and $20.6 million in 2013	0	161,803	769,360
Extinguishment of long-term debt	0	0	(972,468)
Proceeds from initial public offering, net of issuance costs of $20.6 million	0	0	234,944
Borrowings under revolving line of credit	267,300	0	140,800
Payments of revolving line of credit	(243,300)	0	(140,800)
Principal payments of long-term debt	(9,550)	(7,900)	(7,900)
Purchase of non-controlling interest	0	0	(4,138)
Purchase of treasury stock	(128,103)	(221,577)	0
Proceeds from issuance of common stock upon exercise of options	9,811	17,422	11,040
Proceeds from issuance of restricted stock	3,864	4,709	0
Excess tax benefits from stock-based compensation	9,397	9,123	5,923
Net cash (used in) provided by financing activities	(90,581)	(36,420)	36,761
Effect of exchange rates on cash and cash equivalents	(468)	(1,575)	168
Net (decrease) increase in cash and cash equivalents	(76,347)	58,301	(4,524)
Cash and cash equivalents-beginning of period	87,886	29,585	34,109
Cash and cash equivalents-end of period	11,539	87,886	29,585
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash payments of interest	38,110	32,473	34,928
Cash payments of income taxes	49,819	41,713	13,931
Non-cash conversion of Class L common stock	0	0	854,101
Fixed asset purchases recorded in accounts payable and accrued expenses	$ 2,000	$ 3,000	$ 0