Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating activities
Net income (loss)	$ (883)	$ 777
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	1,545	1,535
Employee stock-based compensation	4,359	3,694
Outside director restricted stock awarded in lieu of fees	50	40
Gain on disposal of property and equipment	(4)
Share of loss of equity method investee		45
Changes in assets and liabilities:
Accounts receivable	(4,792)	240
Prepaid expenses and other assets	(771)	(376)
Accounts payable	(898)	(3,799)
Accrued compensation	(1,832)	(1,295)
Accrued expenses and other liabilities	2,049	1,824
Deferred revenues	(321)	(368)
Net cash (used in) provided by operating activities	(1,498)	2,317
Investing activities
Purchases of property and equipment	(2,217)	(2,342)
Purchases of marketable securities	(18,289)	(23,031)
Maturities of marketable securities	20,387	24,560
Net cash used in investing activities	(119)	(813)
Financing activities
Net proceeds from issuance of common stock under stock plans	724	2,618
Repurchase of common stock	(15)
Net cash provided by financing activities	709	2,618
Net (decrease) increase in cash and cash equivalents	(908)	4,122
Cash and cash equivalents at the beginning of the period	18,005	32,869
Cash and cash equivalents at the end of the period	17,097	36,991
Supplemental disclosure of cash flow information
Cash paid for income taxes	$ 108	$ 36