Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities:
Net income (loss)	$ 5,591	$ 10,494	$ (10,216)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Gain on interest rate swap			(101)
Depreciation and amortization	55,691	60,280	62,748
Amortization of deferred rent	577	(112)	(370)
Share-based compensation	22,289	20,024	17,157
Excess tax benefit related to share-based compensation	(2,591)	(9,287)	(6,610)
Provision for doubtful accounts	7,059	5,727	4,751
Amortization of deferred financing costs	1,793	2,317	2,191
Deferred income taxes	(7,027)	(19,546)	(18,021)
Loss on early extinguishment of debt	18,619
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(51,481)	(49,437)	(31,112)
Prepaid expenses and other current assets	(2,145)	(7,505)	(552)
Accounts payable and accrued expenses	10,623	31,642	15,625
Accrued interest expense	(4,422)	236	(487)
Deferred revenue and customer deposits	(2,069)	226	1,676
Other liabilities	(2,477)	140	(324)
Net cash provided by operating activities	50,030	45,199	36,355
Investing activities:
Cash paid for acquisitions, net	(75,235)	(187,402)	(3,318)
Purchases of building, equipment and leasehold improvements, net	(11,190)	(10,894)	(6,544)
Working capital and other settlements for acquisitions	(212)	(2,331)	(569)
Proceeds from foreign currency net investment hedges	7,698	4,006	1,421
Other	(1,499)	(1,542)	(1,144)
Net cash used in investing activities	(80,438)	(198,163)	(10,154)
Financing activities:
Borrowings under senior unsecured notes	500,000
Borrowings under senior secured revolving credit facility	25,478	299,255	142,473
Proceeds from the exercise of options and warrants	14,423	42,437	24,261
Excess tax benefit related to share-based compensation	2,591	9,287	6,610
Repayment of subordinated unsecured notes payable		(333)	(270)
Net borrowings (repayments) under working capital facilities	(3,362)	4,939	2,772
Payment of contingent earnout obligation	(5,064)	(4,362)
Payment of deferred financing costs	(9,035)	(263)	(172)
Payment for early redemption of senior unsecured notes	(14,618)
Purchases of stock for treasury	(21,268)
Repayments under senior secured revolving credit facility	(169,330)	(200,429)	(196,746)
Repayment of senior unsecured notes	(250,000)
Other		(53)
Net cash provided by (used in) financing activities	69,815	150,478	(21,072)
Exchange rate impact on cash and cash equivalents	(1,293)	(592)	(927)
Net increase (decrease) in cash and cash equivalents	38,114	(3,078)	4,202
Cash and cash equivalents, beginning of year	9,751	12,829	8,627
Cash and cash equivalents, end of year	47,865	9,751	12,829
Supplemental disclosures of cash flow information:
Cash paid for interest	36,364	28,876	27,495
Cash paid for income taxes	$ 9,164	$ 3,510	$ 8,967