CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
OPERATING ACTIVITIES:
Net income	$ 75,222	$ 65,315
Adjustments to reconcile net income to net cash provided by operating activities:
Change in fair value of contingent consideration	0	1,204
Stock compensation expense	4,047	4,085
Excess tax benefit of stock options exercised	(4,203)	(5,061)
Depreciation	14,846	12,739
Amortization	6,642	4,979
Deferred income taxes	10,407	11,921
Changes in operating assets and liabilities, net of effect of acquisitions and divestitures:
Accounts receivable	(19,769)	(14,493)
Accounts payable	1,012	2,101
Accrued liabilities	6,618	12,623
Deferred revenues	(1,345)	1,029
Other assets and liabilities	4,693	3,119
Net cash provided by operating activities	98,170	99,561
INVESTING ACTIVITIES:
Payments for acquisitions, net of cash acquired	(18,899)	(28,182)
Proceeds from/ (purchase of) short-term investments	20	(2)
Capital expenditures	(16,480)	(17,049)
Net cash used in investing activities	(35,359)	(45,233)
FINANCING ACTIVITIES:
Repayment of long-term debt and other obligations	(9,996)	(8,275)
Borrowings on foreign bank debt	27,651	4,641
Repayments on foreign bank debt	(62,027)	(4,937)
Borrowings on senior credit facility	291,132	185,434
Repayments on senior credit facility	(337,683)	(238,290)
Payments on capital lease obligations	(837)	(640)
Purchase and cancellation of treasury stock	(7,160)	(2,945)
Proceeds from other issuance of common stock	13,915	12,494
Excess tax benefit of stock options exercised	4,203	5,061
Net cash used in financing activities	(80,802)	(47,457)
Effect of exchange rate changes on cash and cash equivalents	(611)	880
Net (decrease)/ increase in cash and cash equivalents	(18,602)	7,751
Cash and cash equivalents at beginning of period	31,324	22,511
Cash and cash equivalents at end of period	12,722	30,262
NON-CASH ACTIVITIES:
Net issuance of obligations for acquisitions	$ 10,454	$ 14,883