Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities
Net income (loss)	$ (514)	$ 218
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	5,115	4,285
Amortization of premium on investments	70	154
Stock-based compensation expense	3,541	3,299
Recovery of bad debts	(2)	(5)
Deferred income taxes	(2,187)	(693)
Taxes paid related to net share settlement of restricted stock units	(285)	(247)
Changes in operating assets and liabilities, net of effects from acquisition:
Accounts receivable	25	16
Prepaid expenses and other current assets	(3,133)	(643)
Other assets	157	(113)
Accounts payable	(1,300)	1,140
Accrued expenses	5,360	1,592
Deferred revenue	2,101	1,877
Other long-term liabilities	60
Net cash provided by operating activities	9,008	10,880
Cash flows from investing activities
Purchases of marketable securities	(1,909)	(14,270)
Proceeds from maturities of marketable securities	8,634	20,000
Proceeds from sales of marketable securities	4,000	23,581
Acquisitions of businesses, net of cash acquired		(5,750)
Increase in restricted cash	(550)
Acquisition of property and equipment, including costs capitalized for development of internal use software	(4,744)	(5,473)
Net cash provided by investing activities	5,431	18,088
Cash flows from financing activities
Proceeds from issuance of common stock pursuant to the exercise of stock options	182	3,250
Income tax benefit from the exercise of stock options	6	132
Net cash provided by financing activities	188	3,382
Effects of exchange rates on cash	(2)
Net increase in cash and cash equivalents	14,625	32,350
Cash and cash equivalents, beginning of period	67,775	49,589
Cash and cash equivalents, end of period	82,400	81,939
Supplemental disclosure of noncash investing activities:
Capitalization of stock-based compensation	$ 166	$ 224