CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
OPERATING ACTIVITIES:
Net income	$ 313,084	$ 269,941	$ 237,343
Adjustments to reconcile net income to net cash provided by operating activities:
Stock compensation expense	17,457	16,339	15,367
Excess tax benefit of stock options exercised	(17,153)	(30,161)	(17,410)
Depreciation	61,341	54,229	49,777
Amortization	27,067	22,054	16,269
Deferred income taxes	30,930	22,678	31,837
Loss on sale of business	0	4,867	19
Change in fair value of contingent consideration	(2,278)	752	(7,221)
Other, net	3,381	1,677	5,253
Changes in operating assets and liabilities, net of effect of acquisitions and divestitures:
Accounts receivable	(54,767)	(4,329)	(31,821)
Accounts payable	7	406	(9,132)
Accrued liabilities	4,547	24,537	36,289
Deferred revenues	(1,319)	931	(1,997)
Other assets and liabilities	21,170	3,527	(18,469)
Net cash provided by operating activities	403,467	387,448	306,104
INVESTING ACTIVITIES:
Payments for acquisitions, net of cash acquired	(161,936)	(224,367)	(469,209)
Proceeds from/ (purchase of) short-term investments	73	(89)	15,942
Proceeds from sale of business and other assets	0	764	2,371
Capital expenditures	(73,109)	(65,236)	(53,301)
Net cash used in investing activities	(234,972)	(288,928)	(504,197)
FINANCING ACTIVITIES:
Repayment of long-term debt and other obligations	(88,507)	(102,932)	(65,546)
Borrowings on foreign bank debt	218,968	98,620	42,178
Repayments on foreign bank debt	(201,967)	(69,454)	(16,168)
Borrowings on senior credit facility	1,029,718	863,286	1,643,458
Repayments on senior credit facility	(984,979)	(1,167,595)	(1,372,631)
Proceeds from private placement of long-term note	0	250,000	0
Payments of deferred financing costs	0	(956)	(3,740)
Payments on capital lease obligations	(4,024)	(3,192)	(3,333)
Purchase and cancellation of treasury stock	(163,700)	(48,028)	(124,056)
Proceeds from issuance of common stock	42,345	64,461	31,286
Excess tax benefit of stock options exercised	17,153	30,161	17,410
Payments to noncontrolling interests	(1,026)	(5,897)	(10,986)
Net cash used in financing activities	(136,019)	(91,526)	137,872
Effect of exchange rate changes on cash and cash equivalents	(1,809)	1,819	3,456
Net increase/ (decrease) in cash and cash equivalents	30,667	8,813	(56,765)
Cash and cash equivalents at beginning of period	31,324	22,511	79,276
Cash and cash equivalents at end of period	61,991	31,324	22,511
NON-CASH ACTIVITIES:
Issuance of obligations for acquisitions	100,101	97,541	57,560
Issuance of obligations for noncontrolling interests	$ 6,119	$ 8,197	$ 779