CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
OPERATING ACTIVITIES:
Net income	$ 153,665	$ 133,687
Adjustments to reconcile net income to net cash provided by operating activities:
Change in fair value of contingent consideration	(122)	602
Stock compensation expense	7,943	8,217
Excess tax benefit of stock options exercised	(8,373)	(11,523)
Depreciation	30,088	25,630
Amortization	13,175	10,114
Deferred income taxes	13,101	14,546
Changes in operating assets and liabilities, net of effect of acquisitions and divestitures:
Accounts receivable	(42,871)	5,368
Accounts payable	9,619	7,252
Accrued liabilities	(2,231)	(6,409)
Deferred revenues	(548)	2,111
Other assets and liabilities	3,037	(797)
Net cash provided by operating activities	176,483	188,798
INVESTING ACTIVITIES:
Payments for acquisitions, net of cash acquired	(63,401)	(111,716)
Proceeds from/ (purchase of) short-term investments	33	(2)
Capital expenditures	(37,441)	(33,819)
Net cash used in investing activities	(100,809)	(145,537)
FINANCING ACTIVITIES:
Repayment of long-term debt and other obligations	(32,016)	(45,139)
Borrowings on foreign bank debt	92,733	28,208
Repayments on foreign bank debt	(96,512)	(21,392)
Borrowings on senior credit facility	527,469	282,381
Repayments on senior credit facility	(544,183)	(292,455)
Payments of deferred financing costs	0	148
Payments on capital lease obligations	(1,825)	(1,278)
Purchase and cancellation of treasury stock	(66,175)	(2,945)
Payments to noncontrolling interests	0	10
Proceeds from other issuance of common stock	23,667	28,450
Excess tax benefit of stock options exercised	8,373	11,523
Net cash used in financing activities	(88,469)	(12,805)
Effect of exchange rate changes on cash and cash equivalents	(528)	1,246
Net (decrease)/ increase in cash and cash equivalents	(13,323)	31,702
Cash and cash equivalents at beginning of period	31,324	22,511
Cash and cash equivalents at end of period	18,001	54,213
NON-CASH ACTIVITIES:
Net issuance of obligations for acquisitions	$ 22,906	$ 34,328