Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities:
Net income	$ 6,318	$ 1,226
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	6,586	5,782
Bad debt expense	333	153
Loss on disposal of property and equipment	4	1
Stock-based compensation	8,257	4,606
Amortization of premiums and accretion of discounts on investments	324	325
Excess tax benefits from stock-based compensation	(191)	(54)
Deferred income taxes	3,064	(19)
Changes in operating assets and liabilities:
Accounts receivable	(1,892)	367
Prepaid expenses and other assets	(534)	(772)
Accounts payable	(4,619)	(195)
Accrued liabilities	1,846	(558)
Deferred revenues	5,911	4,240
Other noncurrent liabilities	143	92
Net cash provided by operating activities	25,550	15,194
Cash flows from investing activities:
Purchases of investments	(61,442)	(76,907)
Sales and maturities of investments	48,214	64,960
Purchases of property and equipment	(10,407)	(6,524)
Capitalized software development costs	(99)	0
Net cash used in investing activities	(23,734)	(18,471)
Cash flows from financing activities:
Proceeds from exercise of stock options	5,547	3,053
Excess tax benefits from stock-based compensation	191	54
Principal payments under capital lease obligations	0	(536)
Net cash provided by financing activities	5,738	2,571
Effect of exchange rate changes on cash and cash equivalents	0	9
Net increase (decrease) in cash and cash equivalents	7,554	(697)
Cash and cash equivalents at beginning of period	76,504	42,369
Cash and cash equivalents at end of period	84,058	41,672
Non-cash investing and financing activities:
Vesting of early exercised common stock options	$ 11	$ 35