Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities
Net income	$ 78,275	$ 53,538	$ 75,566
Adjustment to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	44,889	50,218	56,991
Amortization of contract acquisition costs	1,680	5,267	3,450
Amortization of debt issuance costs and other	589	672	596
Accretion expense	544	132	90
Provision for doubtful accounts	363	600	1,412
Loss (gain) on disposal of assets	(415)	(617)	1,603
Impairment losses	230	1,958	4,587
Deferred income taxes	1,658	(3,030)	6,066
Excess tax benefit from equity-based awards	(6,491)	(1,783)	(484)
Equity-based compensation expense	15,856	13,372	11,640
(Gain) loss on foreign currency derivatives	1,073	(128)	(192)
Gain on Newgen legal settlement, net of tax	0	(3,542)	0
Changes in assets and liabilities, net of acquisitions:
Accounts receivable	(5,789)	(87)	27,258
Prepaids and other assets	3,578	17,664	(8,651)
Accounts payable and accrued expenses	(16,502)	19,683	(19,142)
Deferred revenue and other liabilities	(5,739)	(19,462)	(118)
Net cash provided by operating activities	113,799	134,455	160,672
Cash flows from investing activities
Proceeds from sale of property, plant, and equipment	2,034	0	0
Proceeds from grant for property, plant and equipment	357	0	785
Purchases of property, plant and equipment	(38,667)	(26,800)	(24,973)
Settlement of foreign currency contracts for net investment hedging	0	0	(1,727)
Payment for contract acquisition costs	(1,758)	0	(3,900)
Investment in deconsolidated subsidiary	0	(3,600)	0
Deposit on pending acquisition	(3,026)	0	0
Acquisitions, net of cash acquired of $14 and $2,202, respectively	(45,871)	(12,798)	0
Net cash used in investing activities	(86,931)	(43,198)	(29,815)
Cash flows from financing activities
Proceeds from line of credit	678,200	1,257,100	920,960
Payments on line of credit	(614,200)	(1,257,100)	(1,001,760)
Payments on capital lease obligations and equipment financing	(2,099)	(3,749)	(2,332)
Dividends distributed to noncontrolling interest	(3,548)	(4,140)	(3,690)
Proceeds from exercise of stock options	14,762	2,792	6,159
Excess tax benefit from equity-based awards	6,491	1,783	484
Purchase of treasury stock	(63,693)	(80,295)	(34,766)
Payments of debt issuance costs	(22)	(2,288)	0
Net cash provided by (used in) financing activities	15,891	(85,897)	(114,945)
Effect of exchange rate changes on cash and cash equivalents	(5,773)	4,601	5,570
Increase in cash and cash equivalents	36,986	9,961	21,482
Cash and cash equivalents, beginning of period	119,385	109,424	87,942
Cash and cash equivalents, end of period	156,371	119,385	109,424
Supplemental disclosures
Cash paid for interest	4,013	2,217	2,775
Cash paid for income taxes	24,336	15,593	24,543
Non-cash investing and financing activities
Acquisition of equipment through installment purchase agreements	0	186	3,971
Landlord incentives credited to deferred rent	0	810	165
Grant income credited to property, plant and equipment	110	0	745
Recognition of asset retirement obligations	$ 278	$ 406	$ 183