Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (33,308,000)	$ (24,592,000)	$ (12,757,000)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	7,069,000	6,870,000	6,324,000
Employee stock-based compensation	16,005,000	16,538,000	17,457,000
Write-off of previously capitalized software costs	635,000		663,000
Impairment of assets held for sale and other long-lived assets	123,000	375,000
Outside director restricted stock awarded in lieu of fees	200,000	230,000	230,000
Gain on disposal of property and equipment	(80,000)	(51,000)
Deferred tax benefit from unrealized gain on available-for-sale marketable securities	(1,548,000)
Impairment of investments			643,000
Changes in assets and liabilities:
Accounts receivable	(2,248,000)	(5,470,000)	(7,193,000)
Prepaid expenses and other assets	(1,292,000)	741,000	(1,448,000)
Accounts payable	949,000	985,000	1,238,000
Accrued compensation and employee benefits	4,531,000	3,824,000	1,886,000
Accrued expenses and other liabilities	(2,963,000)	3,088,000	1,297,000
Deferred revenues	96,000	(251,000)	212,000
Net cash (used in) provided by operating activities	(11,831,000)	2,287,000	8,552,000
Investing activities
Purchases of property and equipment	(23,483,000)	(10,455,000)	(11,008,000)
Proceeds from sale of property and equipment	70,000	122,000	16,000
Purchases of marketable securities	(76,743,000)	(96,800,000)	(107,183,000)
Maturities of marketable securities	106,439,000	94,910,000	116,169,000
Purchase of other investments		(2,000,000)	(5,000,000)
Net cash provided by (used in) investing activities	6,283,000	(14,223,000)	(7,006,000)
Financing activities
Net proceeds from issuance of common stock under stock plans	12,197,000	12,030,000	16,588,000
Withholding taxes related to restricted stock units net share settlement	(3,842,000)	(3,647,000)	(2,845,000)
Repurchase of common stock			(15,000)
Net cash provided by financing activities	8,355,000	8,383,000	13,728,000
Net increase (decrease) in cash and cash equivalents	2,807,000	(3,553,000)	15,274,000
Cash and cash equivalents at the beginning of the period	29,726,000	33,279,000	18,005,000
Cash and cash equivalents at the end of the period	32,533,000	29,726,000	33,279,000
Supplemental disclosure of cash flow information
Cash paid for income taxes	459,000	432,000	336,000
Non-cash investing and financing activities
Accrued purchase of property and equipment	3,847,000	$ 1,809,000	$ 1,138,000
Change in fair value of equity investment	$ 4,269,000