Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (34,853)	$ (56,153)	$ (75,371)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	15,605	15,458	15,774
Stock-based compensation	20,290	32,908	34,754
Change in deferred taxes	338	243	(1,231)
Non-recurring gain	(1,107)	0	0
Loss on sale of property and equipment	103	19	10
(Increase) decrease, net of acquisitions, in:
Accounts receivable, net	12,639	(7,900)	(4,629)
Prepaid expenses and other assets	(307)	(4,084)	(1,437)
Increase (decrease), net of acquisitions, in:
Accounts payable	535	(2,622)	(2,669)
Accrued payroll and related liabilities	300	(883)	101
Other accrued liabilities	(1,266)	139	1,057
Deferred revenue	(12,297)	13,202	30,290
Other long-term liabilities	315	16	373
Net cash provided by (used in) operating activities	295	(9,657)	(2,978)
Cash flows from investing activities:
Payments for purchase of property and equipment	(6,450)	(9,313)	(13,934)
Purchases of marketable securities	(133,314)	(91,987)	(111,700)
Sales of marketable securities	25,383	36,174	40,772
Maturities of marketable securities	104,317	57,324	84,934
Acquisitions, net of cash acquired	0	0	(11,047)
Net cash used in investing activities	(10,064)	(7,802)	(10,975)
Cash flows from financing activities:
Proceeds from exercise of stock options	1,345	4,250	6,947
Taxes paid related to net share settlement of equity awards	(1,058)	(1,758)	(1,074)
Repayments of term loans	(2,400)	(2,400)	(2,400)
Earnout payment for prior acquisition	0	(576)	0
Non-recurring gain	1,107	0	0
Net cash provided by (used in) financing activities	(1,006)	(484)	3,473
Net decrease in cash and cash equivalents	(10,775)	(17,943)	(10,480)
Effect of exchange rate changes	51	122	(60)
Cash and cash equivalents, beginning of period	20,594	38,415	48,955
Cash and cash equivalents, end of period	$ 9,870	$ 20,594	$ 38,415