CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	[4]	Dec. 31, 2017 USD ($)	[4]	Dec. 31, 2016 USD ($)	[4]
Operating activities:
Net income	$ 10,617	[1],[2],[3]	$ 98,548	[1],[2],[3]	$ 45,015	[1],[2],[3]
Adjustment to reconcile net income to cash provided by operating activities:
Deferred income taxes	(30,898)		(2,780)		(4,398)
Amortization of intangible assets and depreciation	25,295		24,713		24,137
Amortization of deferred contract costs	17,271		12,106		11,574
Amortization of investments	1,596		1,381		1,862
Stock-based compensation expense	63,862		53,313		40,821
Foreign currency transaction (gain) loss	(2,421)	[2]	6,413	[2]	(9,360)	[2]
Other non-cash	(1,678)		(1,383)		(1,382)
Change in operating assets and liabilities:
Accounts receivable, unbilled revenue, and contract assets	25,779		(30,379)		(49,503)
Income taxes receivable and other current assets	(6,068)		(13,393)		(10,818)
Accounts payable, accrued compensation, and accrued expenses	20,798		14,473		1,531
Deferred revenue	28,951		14,636		2,639
Deferred contract costs	(44,036)		(18,738)		(12,497)
Other long-term assets and liabilities	(4,712)		(675)		253
Cash provided by operating activities	104,356		158,235		39,874
Investing activities:
Purchases of investments	(69,494)		(27,718)		(23,969)
Proceeds from maturities and called investments	33,991		26,997		22,788
Sales of investments	0		0		62,210
Payments for acquisitions, net of cash acquired	(800)		(297)		(49,113)
Investment in property and equipment	(11,893)		(13,741)		(19,088)
Cash used in investing activities	(48,196)		(14,759)		(7,172)
Financing activities:
Dividend payments to shareholders	(9,432)		(9,277)		(9,174)
Common stock repurchases for tax withholdings for net settlement of equity awards	(37,594)		(40,617)		(15,294)
Common stock repurchases under stock repurchase program	(54,434)		(4,335)		(27,248)
Cash used in financing activities	(101,460)		(54,229)		(51,716)
Effect of exchange rate on cash and cash equivalents	(2,557)		2,438		(3,418)
Net (decrease) increase in cash and cash equivalents	(47,857)		91,685		(22,432)
Cash and cash equivalents, beginning of period	162,279	[5]	70,594		93,026
Cash and cash equivalents, end of period	114,422	[5]	162,279	[5]	70,594
Supplemental disclosures:
Income taxes paid (refunded)	6,630		(2,322)		28,844
Non-cash investing and financing activity:
Dividends payable	$ 2,363		$ 2,344		$ 2,298

[1] On January 1, 2018, the Company adopted the ASC 606 revenue recognition standard and adjusted prior periods to conform. See "Note 2. Significant Accounting Policies" for additional information.

[2] On January 1, 2018, the Company adopted the ASC 606 revenue recognition standard and adjusted prior periods to conform. See "Note 2. Significant Accounting Policies" for additional information.

[3] On January 1, 2018, the Company adopted the ASC 606 revenue recognition standard and adjusted prior periods to conform. See "Note 2. Significant Accounting Policies" for additional information.

[4] On January 1, 2018, the Company adopted the ASC 606 revenue recognition standard and adjusted prior periods to conform. See "Note 2. Significant Accounting Policies" for additional information.

[5] On January 1, 2018, the Company adopted the ASC 606 revenue recognition standard and adjusted prior periods to conform. See "Note 2. Significant Accounting Policies" for additional information.