Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities
Net loss	$ (46,195)	$ (30,555)	$ (33,227)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,548	2,349	1,571
Stock-based compensation	18,371	10,252	4,287
Remeasurement of convertible preferred stock warrant liability	0	(90)	2,225
Others	378	178	146
Changes in operating assets and liabilities:
Accounts receivable, net	1,871	(7,115)	(4,859)
Inventories	(2,415)	(1,544)	32
Prepaid expenses and other current assets	(1,275)	(733)	(241)
Other assets	(257)	(98)	26
Accounts payable	5,237	1,295	1,002
Accrued liabilities	3,067	1,563	2,494
Other liabilities	(394)	165	297
Deferred revenue	13,107	15,585	13,867
Net cash used in operating activities	(4,957)	(8,748)	(12,380)
Cash flows from investing activities
Purchases of property and equipment	(2,270)	(2,385)	(2,910)
Capitalized software development costs	(1,913)	(4,364)	0
Maturities and sales of short-term investments	2,498	0	0
Purchases of short-term investments	(49,223)	0	0
Net cash used in investing activities	(50,908)	(6,749)	(2,910)
Cash flows from financing activities
Proceeds from initial public offering, net of underwriting discounts	0	80,213	0
Payment of offering costs	0	(4,007)	(1,408)
Net proceeds from issuance of convertible preferred stock	0	0	9,943
Proceeds from exercise of convertible preferred stock warrants	0	907	692
Proceeds from exercise of vested stock options	1,524	1,721	1,169
Proceeds from early exercise of stock options, net of repurchases	0	0	813
Proceeds from employee stock purchase plan	5,196	0	0
Payment for shares repurchased for tax withholdings on vesting of restricted stock units	(3,158)	(316)	0
Proceeds from issuance of debt	10,000	0	10,000
Payments for debt issuance cost	0	0	(481)
Repayments of debt	10,000	0	0
Net cash provided by financing activities	3,562	78,518	20,728
Net increase (decrease) in cash and cash equivalents	(52,303)	63,021	5,438
Cash and cash equivalents at beginning of period	98,044	35,023	29,585
Cash and cash equivalents at end of period	45,741	98,044	35,023
Supplemental disclosure of cash flow information
Income taxes paid	519	420	406
Interest paid	984	1,428	540
Supplemental disclosure of noncash investing and financing activities
Conversion of convertible preferred stock warrants to common stock warrants upon IPO	0	611	0
Unpaid property and equipment purchased	60	312	164
Unpaid capitalized software development costs	94	439	0
Reclassification of the convertible preferred stock warrant liability to additional paid-in capital on the exercise of the convertible preferred stock warrants	0	3,202	1,755
Vesting of early exercised stock options	45	435	481
Offering costs for common stock not yet paid	0	0	2,090
Stock-based compensation in capitalized software development	$ 257	$ 445	$ 0