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	$ (66,837)	$ (85,516)	$ (64,899)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	32,392	27,512	15,086
Accretion of debt discount and amortization of debt issuance costs	9,130	8,691	8,274
Purchased investment premium, net of amortization	240	262	816
Net foreign currency (gain) loss	(7)	1,584	1,656
Stock-based compensation expense	54,699	43,081	33,680
Deferred income taxes	(736)	(105)	(7)
Changes in operating assets and liabilities:
Accounts receivable	(38,092)	(21,837)	(18,674)
Deferred commissions	(2,543)	(10,296)	(10,097)
Prepaid expenses and other assets	(3,623)	(2,575)	1,245
Accounts payable	5,939	4,444	4,562
Accrued expenses	3,727	14,724	6,446
Deferred revenue	43,379	64,774	55,216
Other liabilities	(2,416)	(947)	(295)
Net cash provided by operating activities	35,252	43,796	33,009
Cash flows from investing activities:
Purchases of investments	(210,534)	(220,383)	(124,191)
Maturities of investments	151,533	138,360	203,078
Capital expenditures	(6,228)	(15,633)	(11,025)
Capitalized software costs	(16,409)	(13,283)	(9,529)
Cash paid for acquisition, net of cash acquired	0	0	(43,328)
Net cash (used in) provided by investing activities	(81,638)	(110,939)	15,005
Cash flows from financing activities:
Repayment of debt	0	(352)	(559)
Principal payments under capital lease obligations	(33)	(202)	(886)
Proceeds from employee stock plans	23,548	11,559	12,285
Net cash provided by financing activities	23,515	11,005	10,840
Effect of exchange rate changes on cash and cash equivalents	(1,520)	(2,728)	(1,880)
Net (decrease) increase in cash and cash equivalents	(24,391)	(58,866)	56,974
Cash and cash equivalents at beginning of period	107,691	166,557	109,583
Cash and cash equivalents at end of period	83,300	107,691	166,557
Supplemental cash flow information:
Cash paid for interest	3,796	1,915	3,880
Cash paid for income taxes	2,334	1,520	546
Proceeds from employee stock plans received in advance of stock issuance	489	193	0
Non-cash investing and financing activities:
Capitalized assets financed by accounts payable and accrued expenses	2,080	705	2,925
Capitalized stock-based compensation	$ 4,252	$ 2,833	$ 1,563