Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating activities
Net income (loss)	$ 7,846	$ 4,288	$ (9,411)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	7,310	7,180	6,591
Employee stock-based compensation	11,735	10,344	10,155
Non-employee stock-based compensation		15	80
Gain on disposal of property and equipment	(7)	(45)	(44)
Share of loss of equity method investee	165
Changes in assets and liabilities:
Accounts receivable	(6,771)	(3,183)	(2,316)
Prepaid expenses and other assets	(633)	(2,365)	(1,127)
Accounts payable	3,057	2,664	(594)
Accrued compensation	2,222	1,164	2,031
Accrued expenses and other liabilities	(1,250)	938	1,021
Deferred revenues	(1,203)	583	(1,560)
Net cash provided by operating activities	22,471	21,583	4,826
Investing activities
Purchase of property and equipment	(6,183)	(4,442)	(3,744)
Purchase of marketable securities	(133,993)	(84,303)	(60,318)
Maturities of marketable securities	112,003	87,005	57,225
Purchase of other investments	(2,300)	(500)
Net cash used in investing activities	(30,473)	(2,240)	(6,837)
Financing activities
Principal payments of notes payable		(225)	(1,814)
Proceeds from issuance of common stock under stock plans	9,688	2,983	1,736
Net cash provided by (used in) financing activities	9,688	2,758	(78)
Net increase (decrease) in cash and cash equivalents	1,686	22,101	(2,089)
Cash and cash equivalents at the beginning of period	31,183	9,082	11,171
Cash and cash equivalents at the end of period	32,869	31,183	9,082
Supplemental disclosure of cash flow information
Cash paid for interest		13	120
Cash paid for income taxes	$ 243	$ 622	$ 28