Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net income	$ 193,582	$ 175,635	$ 183,766
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangibles	61,969	47,131	39,412
Stock-based compensation expense	46,661	46,149	38,845
Excess tax benefits from stock-based compensation exercises	0	(13,860)	(20,193)
Deferred taxes	(2,648)	344	(759)
Gain on extinguishment of debt	(2,500)	0	0
Amortization and write-off of debt issue costs	3,082	1,512	2,645
Changes in assets and liabilities:
Fees receivable, net	(68,661)	(44,476)	(76,424)
Deferred commissions	(18,673)	(13,236)	(12,340)
Prepaid expenses and other current assets	(21,604)	(13,268)	(3,017)
Other assets	20,005	(14,733)	(7,139)
Deferred revenues	97,979	91,840	105,354
Accounts payable, accrued, and other liabilities	56,440	82,523	96,629
Cash provided by operating activities	365,632	345,561	346,779
Investing activities:
Additions to property, equipment and leasehold improvements	(49,863)	(46,128)	(38,486)
Acquisitions (net of cash acquired)	(34,186)	(196,229)	(124,291)
Cash used in investing activities	(84,049)	(242,357)	(162,777)
Financing activities:
Proceeds from ESP Plan	9,250	7,499	7,767
Proceeds from borrowings	715,000	440,000	400,000
Payments on debt	(835,000)	(20,000)	(200,000)
Purchases of treasury stock	(58,961)	(509,049)	(432,006)
Fees paid for debt refinancing	(4,975)	0	(4,624)
Excess tax benefits from stock-based compensation exercises	0	13,860	20,193
Cash used by financing activities	(174,686)	(67,690)	(208,670)
Net increase (decrease) in cash and cash equivalents	106,897	35,514	(24,668)
Effects of exchange rates on cash and cash equivalents	(5,640)	(27,840)	(34,020)
Cash and cash equivalents, beginning of period	372,976	365,302	423,990
Cash and cash equivalents, end of period	474,233	372,976	365,302
Cash paid during the period for:
Interest	23,400	21,200	10,600
Income taxes, net of refunds received	$ 86,300	$ 83,500	$ 70,100