CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Operating activities
Net (loss) income	$ (90,433)	$ 10,617	$ 98,548
Adjustments to reconcile net (loss) income to cash (used in) provided by operating activities
Stock-based compensation expense	80,909	63,862	53,313
Deferred income taxes	(49,317)	(30,898)	(2,780)
Amortization of deferred contract costs	29,152	17,271	12,106
Lease expense	14,497	0	0
Amortization of intangible assets and depreciation	21,396	25,295	24,713
Amortization of investments	800	1,596	1,381
Foreign currency transaction loss (gain)	2,335	(2,421)	6,413
Other non-cash	(521)	(1,678)	(1,383)
Change in operating assets and liabilities:
Accounts receivable, unbilled revenue, and contract assets	1,088	25,779	(30,379)
Income taxes receivable and other current assets	(6,344)	(6,068)	(13,393)
Accounts payable, accrued compensation, and accrued expenses	25,670	20,798	14,473
Deferred revenue	1,937	28,951	14,636
Deferred contract costs	(49,746)	(44,036)	(18,738)
Other long-term assets and liabilities	(23,588)	(4,712)	(675)
Cash (used in) provided by operating activities	(42,165)	104,356	158,235
Investing activities
Purchases of investments	(11,424)	(69,494)	(27,718)
Proceeds from maturities and called investments	13,634	33,991	26,997
Sales of investments	89,406	0	0
Payments for acquisitions, net of cash acquired	(10,934)	(800)	(297)
Investment in property and equipment	(10,608)	(11,893)	(13,741)
Cash provided by (used in) investing activities	70,074	(48,196)	(14,759)
Financing activities
Dividend payments to shareholders	(9,486)	(9,432)	(9,277)
Proceeds from revolving credit facility	45,000	0	0
Payments on revolving credit facility	(45,000)	0	0
Common stock repurchases for tax withholdings for net settlement of equity awards	(42,637)	(37,594)	(40,617)
Common stock repurchases under stock repurchase program	(22,135)	(54,434)	(4,335)
Cash (used in) financing activities	(74,258)	(101,460)	(54,229)
Effect of exchange rate changes on cash and cash equivalents	290	(2,557)
Effect of exchange rate changes on cash and cash equivalents (before ASU 2016-18)			2,438
Net (decrease) increase in cash and cash equivalents	(46,059)	(47,857)	91,685
Cash and cash equivalents, beginning of period	114,422	162,279	70,594
Cash and cash equivalents, end of period	68,363	114,422	162,279
Supplemental disclosures
Income taxes paid (refunded)	4,745	6,630	(2,322)
Non-cash investing and financing activity:
Dividends payable	$ 2,388	$ 2,363	$ 2,344