UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities:
Net income	$ 9,005	$ 5,935
Adjustments to reconcile net income to cash provided by operating activities:
Excess tax benefits from exercise or vesting of equity awards	(1,398)	(822)
Deferred income taxes	650	(3)
Depreciation and amortization	5,466	5,624
Stock-based compensation expense	8,935	6,269
Foreign currency transaction (gain) loss	(1,376)	2,962
Other non-cash	2,712	161
Change in operating assets and liabilities:
Trade accounts receivable	6,697	(299)
Income taxes receivable and other current assets	(201)	(4,403)
Accounts payable and accrued expenses	(23,427)	(21,621)
Deferred revenue	1,129	33,919
Other long-term assets and liabilities	450	(201)
Cash provided by operating activities	8,642	27,521
Investing activities:
Purchases of marketable securities	(8,193)	(18,120)
Proceeds from maturities and called marketable securities	15,890	16,549
Sales of marketable securities	6,179
Payments for acquisitions, net of cash acquired	(255)	(535)
Investment in property and equipment	(4,251)	(3,275)
Cash provided by (used in) investing activities	9,370	(5,381)
Financing activities:
Issuance of common stock for share-based compensation plans	44	146
Excess tax benefits from exercise or vesting of equity awards	1,398	822
Dividend payments to shareholders	(2,297)	(2,294)
Common stock repurchases for tax withholdings for net settlement of equity awards	(5,682)	(2,584)
Common stock repurchases under share repurchase programs	(11,887)	(2,427)
Cash used in financing activities	(18,424)	(6,337)
Effect of exchange rates on cash and cash equivalents	(434)	(2,908)
Net (decrease) increase in cash and cash equivalents	(846)	12,895
Cash and cash equivalents, beginning of period	93,026	114,585
Cash and cash equivalents, end of period	$ 92,180	$ 127,480