Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities
Net loss	$ (35,852)	$ (26,482)	$ (17,423)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation	4,722	2,642	1,344
Amortization of internal-use software	1,156	525	456
Loss (gain) on disposal of property and equipment	10	(7)	65
Noncash interest expense related to warrants issued in connection with debt	251	159	56
Noncash expense related to warrants issued in connection with service agreement		60	49
Change in the valuation of outstanding preferred stock warrants	238	362	73
Stock-based compensation related to stock option grants	5,218	2,358	697
Stock-based compensation related to preferred stock financing		2,590
Provision for bad debt	359	296	289
Deferred income tax benefit	(91)	(108)
Excess tax benefits from stock-based award activities	(119)	(192)
Other noncash expenses	245	292	211
Changes in operating assets and liabilities
Accounts receivable	(2,392)	(3,674)	(5,452)
Prepaid expenses and other current assets	(881)	(550)	(58)
Other assets	(524)	(55)	(291)
Accounts payable	75	(208)	(54)
Deferred revenue	1,948	445	(46)
Accrued expenses and other liabilities	2,240	2,452	3,594
Net cash used in operating activities	(23,397)	(19,095)	(16,490)
Investing activities
Purchases of property and equipment	(5,023)	(5,507)	(2,332)
Capitalization of internally developed software	(3,216)	(1,743)	(1,028)
Net cash used in investing activities	(8,239)	(7,250)	(3,360)
Financing activities
Proceeds from issuance of common stock in initial public offering, net of issuance costs	109,414	(107)
Proceeds from issuance of note payable, net of issuance costs	1,667	8,631	5,529
Repayment of note payable	(9,660)	(4,334)	(2,012)
Redemption of common stock		(4,488)
Redemption of unvested shares subject to repurchase	(77)	(48)
Proceeds from issuance of convertible, preferred stock, net of issuance costs		54,196	15,934
Proceeds from common stock purchase agreements		500
Proceeds from exercise of common stock warrants			155
Proceeds from exercise of common stock options	1,541	1,624	791
Proceeds from employee stock purchase plan	1,499
Excess tax benefits from stock-based award activities	119	192
Net cash provided by financing activities	104,503	56,166	20,397
Net increase in cash and cash equivalents	72,867	29,821	547
Cash and cash equivalents
Beginning of period	31,540	1,719	1,172
End of period	104,407	31,540	1,719
Supplemental disclosures of other cash flow information
Cash paid for interest	201	453	264
Cash paid for taxes	276	176	8
Supplemental disclosure of noncash investing and financing activities
Conversion of convertible preferred stock to common stock	105,710
Acquisition of equipment through capital lease	3,167
Conversion of warrant to purchase convertible preferred stock to common stock warrant	745
Accounts payable related purchases of property and equipment	208	533	301
Accrued but unpaid debt issuance costs	38	57
Unpaid deferred initial public offering costs		944
Other receivables for stock option exercises		$ 49