Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income (loss)	$ 10,494,000	$ (10,216,000)	$ (14,939,000)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Gain on interest rate swap		(101,000)	(225,000)
Depreciation and amortization	60,280,000	62,748,000	58,551,000
Amortization of deferred rent	(112,000)	(370,000)	(82,000)
Share-based compensation	20,024,000	17,157,000	13,756,000
Excess tax benefit related to share-based compensation	(9,287,000)	(6,610,000)	(2,853,000)
Provision for doubtful accounts	5,727,000	4,751,000	2,852,000
Amortization of deferred financing costs	2,317,000	2,191,000	2,190,000
Deferred income taxes	(19,546,000)	(18,021,000)	(21,201,000)
Other			(31,000)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(49,437,000)	(31,112,000)	(24,666,000)
Prepaid expenses and other current assets	(7,505,000)	(552,000)	(64,000)
Accounts payable and accrued expenses	31,642,000	15,625,000	8,300,000
Accrued interest expense	236,000	(487,000)	671,000
Deferred revenue and customer deposits	226,000	1,676,000	2,425,000
Other liabilities	140,000	(324,000)	93,000
Net cash provided by operating activities	45,199,000	36,355,000	24,777,000
Investing activities:
Cash paid for acquisitions, net	(187,402,000)	(3,318,000)	(108,970,000)
Purchases of building, equipment and leasehold improvements, net	(10,894,000)	(6,544,000)	(5,841,000)
Working capital and other settlements for acquisitions	(2,331,000)	(569,000)	427,000
Proceeds from foreign currency net investment hedges	4,006,000	1,421,000
Other	(1,542,000)	(1,144,000)
Net cash used in investing activities	(198,163,000)	(10,154,000)	(114,384,000)
Financing activities:
Borrowings under senior secured revolving credit facility	299,255,000	142,473,000	170,640,000
Proceeds from the exercise of options and warrants	42,437,000	24,261,000	2,258,000
Excess tax benefit related to share-based compensation	9,287,000	6,610,000	2,853,000
Net borrowings (repayments) under working capital facilities	4,939,000	2,772,000	(6,279,000)
Purchases of stock for treasury			(387,000)
Payment of deferred financing costs	(263,000)	(172,000)	(1,074,000)
Repayment of subordinated unsecured notes payable	(333,000)	(270,000)	(2,193,000)
Repayment of contingent earnout obligation	(4,362,000)
Repayments under senior secured revolving credit facility	(200,429,000)	(196,746,000)	(76,000,000)
Other	(53,000)		(94,000)
Net cash provided by (used in) financing activities	150,478,000	(21,072,000)	89,724,000
Exchange rate impact on cash and cash equivalents	(592,000)	(927,000)	94,000
Net increase (decrease) in cash and cash equivalents	(3,078,000)	4,202,000	211,000
Cash and cash equivalents, beginning of year	12,829,000	8,627,000	8,416,000
Cash and cash equivalents, end of year	9,751,000	12,829,000	8,627,000
Supplemental disclosures of cash flow information:
Cash paid for interest	28,876,000	27,495,000	25,214,000
Cash paid for income taxes	3,510,000	8,967,000	8,913,000
Issuance of Common Stock for Acquisitions [Member]
Financing activities:
Issuance of common stock for acquisitions			$ 85,000