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	$ 65,885	$ 77,417	$ 71,471
Adjustment to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	63,808	56,538	46,064
Amortization of contract acquisition costs	900	856	1,160
Amortization of debt issuance costs	712	705	659
Imputed interest expense and fair value adjustments to contingent consideration	716	(6,233)	3,301
Provision for doubtful accounts	1,465	633	695
Gain on disposal of assets	(166)	141	0
Impairment losses	8,100	373	1,205
Deferred income taxes	9,317	9,514	6,892
Excess tax benefit from equity-based awards	(662)	(1,399)	(1,343)
Equity-based compensation expense	11,304	11,307	13,234
Loss (gain) on foreign currency derivatives	(1,469)	(1,548)	234
Loss on deconsolidation of subsidiary, net of cash of zero, zero and $897, respectively	0	0	2,758
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	(19,867)	(41,005)	7,291
Prepaids and other assets	(5,379)	(5,300)	(5,374)
Accounts payable and accrued expenses	11,941	(8,115)	(2,549)
Deferred revenue and other liabilities	(12,855)	206	(7,718)
Net cash provided by operating activities	133,750	94,090	137,979
Cash flows from investing activities
Proceeds from Sale of Productive Assets	202	135	0
Purchases of property, plant and equipment, net of acquisitions	(66,595)	(67,641)	(50,364)
Investments in non-marketable equity investments	(9,000)	0	0
Acquisitions, net of cash acquired of zero and $812, respectively	(1,776)	(24,416)	(9,166)
Net cash used in investing activities	(77,169)	(91,922)	(59,530)
Cash flows from financing activities
Proceeds from line of credit	2,262,350	2,077,400	1,533,550
Payments on line of credit	(2,262,350)	(2,077,400)	(1,541,550)
Proceeds from other debt	0	0	3,709
Payments on other debt	(3,222)	(4,504)	(5,789)
Payments of contingent consideration related to acquisitions	(11,883)	(8,547)	0
Dividends paid to shareholders	(17,423)	0	0
Dividends distributed to noncontrolling interest	(4,593)	(5,962)	(4,455)
Proceeds from exercise of stock options	825	443	862
Excess tax benefit from equity-based awards	662	1,399	1,343
Payments of debt issuance costs	(35)	0	(1,800)
Purchase of treasury stock	(17,231)	(57,074)	(56,532)
Net cash used in financing activities	(52,900)	(74,245)	(70,662)
Effect of exchange rate changes on cash and cash equivalents	(20,693)	(8,624)	(14,255)
(Decrease) increase in cash and cash equivalents	(17,012)	(80,701)	(6,468)
Cash and cash equivalents, beginning of period	77,316	158,017	164,485
Cash and cash equivalents, end of period	60,304	77,316	158,017
Supplemental disclosures
Cash paid for interest	6,052	5,404	4,220
Cash paid for income taxes	15,178	14,545	16,757
Non-cash investing and financing activities
Acquisition of long lived assets through capital leases	10,492	696	0
Acquisition of equipment through increase in accounts payable, net	386	4,170	2,762
Landlord incentives credited to deferred rent	0	0	1,016
Contract acquisition costs credited to accounts receivable	$ 1,055	$ 471	$ 1,000