Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 1,266	$ 270
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	5,782	4,493
Bad debt expense	153	68
Loss on disposal of property and equipment	1	9
Stock-based compensation	4,606	2,187
Amortization of premiums on investments	325	115
Excess tax benefits from stock-based compensation	(54)	0
Changes in operating assets and liabilities:
Accounts receivable	367	1,549
Prepaid expenses and other assets	(787)	429
Accounts payable	(207)	477
Accrued liabilities	(618)	1,170
Deferred revenues	4,240	2,545
Other noncurrent liabilities	101	(442)
Net cash provided by operating activities	15,175	12,870
Cash flows from investing activities:
Purchases of investments	(76,907)	(75,048)
Sales and maturities of investments	64,960	100,624
Purchases of property and equipment	(6,495)	(6,238)
Release of restricted cash	0	114
Net cash (used in) provided by investing activities	(18,442)	19,452
Cash flows from financing activities:
Proceeds from exercise of stock options	3,082	2,163
Excess tax benefits from stock-based compensation	54	0
Principal payments under capital lease obligations	(536)	(655)
Net cash provided by financing activities	2,600	1,508
Effect of exchange rate changes on cash and cash equivalents	(30)	(96)
Net (decrease) increase in cash and cash equivalents	(697)	33,734
Cash and cash equivalents at beginning of period	42,369	34,885
Cash and cash equivalents at end of period	41,672	68,619
Non-cash investing and financing activities:
Purchases of property and equipment recorded in accrued liabilities	0	2,450
Vesting of early exercised common stock options	$ 35	$ 144