CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities
Net loss	$ (26,994)	$ (27,171)
Adjustments to reconcile net loss to net cash provided by operating activities
Depreciation and amortization	7,923	6,526
Share-based compensation	19,213	17,695
Other	697	403
Changes in operating assets and liabilities:
Accounts receivable	(2,316)	1,898
Prepaid expenses and other current assets	(513)	862
Other assets and liabilities	(332)	(383)
Accounts payable	1,958	(1,851)
Accrued liabilities	2,524	2,307
Accrued compensation and related benefits	(2,596)	(2,066)
Deferred revenue	7,585	6,369
Net cash provided by operating activities	7,149	4,589
Cash flows from investing activities
Purchases of property and equipment	(4,791)	(3,249)
Internal-use software development costs	(1,852)	(1,351)
Purchases of marketable securities	(40,758)	(20,795)
Proceeds from maturities of marketable securities	31,654	10,051
Proceeds from sale of marketable securities	8,602	7,604
Net cash used in investing activities	(7,145)	(7,740)
Cash flows from financing activities
Proceeds from exercise of employee stock options	11,689	1,915
Proceeds from employee stock purchase plan	3,844	3,144
Taxes paid related to net share settlement of equity awards	(154)	(189)
Net cash provided by financing activities	15,379	4,870
Effect of exchange rate changes on cash and cash equivalents	198	(154)
Net increase in cash and cash equivalents	15,581	1,565
Cash and cash equivalents at beginning of period	93,677	216,226
Cash and cash equivalents at end of period	109,258	217,791
Supplemental cash flow data:
Cash paid for interest and income taxes	196	168
Non-cash investing and financing activities:
Vesting of early exercised stock options	115	232
Balance of property and equipment in accounts payable and accrued expenses	1,460	2,345
Share-based compensation capitalized in internal-use software development costs	$ 694	$ 563