CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING ACTIVITIES:
Net income	$ 268,013	$ 328,146	$ 313,084
Adjustments to reconcile net income to net cash provided by operating activities:
Stock compensation expense	21,750	17,773	17,457
Excess tax benefit of stock options exercised	(16,897)	(17,906)	(17,153)
Depreciation	81,914	71,924	61,341
Amortization	45,498	32,692	27,067
Deferred income taxes	(10,294)	16,550	30,930
Other, net	7,467	8,932	1,103
Changes in operating assets and liabilities, net of effect of acquisitions and divestitures:
Accounts receivable	(55,890)	(34,116)	(54,767)
Accounts payable	26,366	(5,712)	7
Accrued liabilities	26,060	21,279	4,547
Deferred revenues	(4,615)	1,017	(1,319)
Other assets and liabilities	956	7,921	23,010
Net cash provided by operating activities	390,328	448,500	405,307
INVESTING ACTIVITIES:
Payments for acquisitions, net of cash acquired	(2,419,437)	(374,321)	(161,936)
Proceeds from/ (purchases of) investments	294	(1,957)	73
Capital expenditures	(114,761)	(86,496)	(73,109)
Net cash used in investing activities	(2,533,904)	(462,774)	(234,972)
FINANCING ACTIVITIES:
Repayments of long-term debt and other obligations	(93,172)	(101,231)	(88,507)
Proceeds from foreign bank debt	53,747	205,086	218,968
Repayments of foreign bank debt	(87,308)	(193,284)	(201,967)
Proceeds from term loan	1,550,000	0	0
Repayment of term loan	(300,000)	0	0
Proceeds from private placement of long-term note	600,000	0	0
Repayments of private placement of long-term note	(100,000)	0	0
Proceeds from senior credit facility	1,907,402	1,413,026	1,029,718
Repayments of senior credit facility	(2,004,385)	(1,216,031)	(984,979)
Payments of capital lease obligations	(3,865)	(5,826)	(4,024)
Payments of deferred financing costs	(9,903)	(2,280)	0
Payment of cash flow hedge	(8,833)	0	0
Purchases and cancellations of treasury stock	(130,576)	(194,066)	(163,700)
Proceeds from issuance of mandatory convertible preferred stock	746,900	0	0
Dividends paid on mandatory convertible preferred stock	(10,106)	0	0
Proceeds from issuance of common stock	60,124	51,852	42,345
Excess tax benefit of stock options exercised	16,897	17,906	17,153
Payments to noncontrolling interests	(5,714)	(5,201)	(1,026)
Net cash provided by/ (used in) financing activities	2,181,208	(30,049)	(136,019)
Effect of exchange rate changes on cash and cash equivalents	(4,234)	(608)	(1,809)
Net increase/ (decrease) in cash and cash equivalents	33,398	(44,931)	32,507
Cash and cash equivalents at beginning of period	22,236	67,167	34,660
Cash and cash equivalents at end of period	55,634	22,236	67,167
NON-CASH ACTIVITIES:
Issuances of obligations for acquisitions	80,189	145,938	100,101
Issuances of obligations for noncontrolling interest	$ 0	$ 0	$ 6,119