CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net loss	$ (103,799)	$ (84,052)	$ (67,415)
Adjustments to reconcile net loss to net cash provided by operating activities
Depreciation and amortization	27,506	19,744	11,456
Share-based compensation	73,779	52,556	32,139
Excess tax benefit from share-based award activity	(337)	(449)	(334)
Other	3,106	1,457	337
Changes in operating assets and liabilities:
Accounts receivable	(11,808)	(14,989)	(3,846)
Prepaid expenses and other current assets	(6,286)	(5,510)	(1,444)
Other assets and liabilities	(3,887)	(3,204)	1,742
Accounts payable	(3,486)	2,017	947
Accrued liabilities	5,261	2,204	351
Accrued compensation and related benefits	6,055	1,706	5,767
Deferred revenue	38,418	33,853	22,390
Net cash provided by operating activities	24,522	5,333	2,090
Cash flows from investing activities
Purchases of property and equipment	(20,647)	(22,989)	(21,665)
Internal-use software development costs	(6,310)	(4,705)	(8,013)
Purchases of marketable securities	(249,048)	(70,303)	(54,330)
Proceeds from maturities of marketable securities	39,690	36,982	10,450
Proceeds from sale of marketable securities	53,951	32,152	4,004
Decrease in restricted cash	0	0	153
Net cash used in investing activities	(182,364)	(72,721)	(71,297)
Cash flows from financing activities
Proceeds from initial public offering, net of issuance costs	0	0	103,090
Proceeds from follow-on public offering, net of issuance costs	0	190,094	0
Proceeds from exercise of employee stock options	25,412	10,609	7,229
Proceeds from employee stock purchase plan	11,004	9,526	4,404
Taxes paid related to net share settlement of equity awards	(803)	(609)	(2,117)
Excess tax benefit from share-based award activity	337	449	334
Principal payments on debt	(323)	(6,952)	(20,748)
Proceeds from issuance of debt	0	0	3,940
Principal payments on capital lease obligations	0	(10)	(364)
Net cash provided by financing activities	35,627	203,107	95,768
Effect of exchange rates changes on cash and cash equivalents	(334)	242	(21)
Net increase (decrease) in cash and cash equivalents	(122,549)	135,961	26,540
Cash and cash equivalents at the beginning of period	216,226	80,265	53,725
Cash and cash equivalents at the end of period	93,677	216,226	80,265
Supplemental cash flow data:
Cash paid for interest and income taxes	1,678	793	1,056
Non-cash investing and financing activities:
Issuance of common stock for the acquisition of Zopim	0	0	10,892
Vesting of early exercised stock options	628	1,048	1,512
Balance of property and equipment in accounts payable and accrued expenses	3,610	3,179	484
Property and equipment acquired through tenant improvement allowances	237	174	3,932
Share-based compensation capitalized in internal-use software development costs	2,365	2,085	2,476
We Are Cloud, Inc
Cash flows from investing activities
Cash paid for the acquisition, net of cash acquired	0	(42,758)	0
Zopim
Cash flows from investing activities
Cash paid for the acquisition, net of cash acquired	$ 0	$ (1,100)	$ (1,896)