CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (16,370)	$ (13,373)
Adjustments to reconcile net loss to net cash provided by operating activities:
Stock-based compensation expense	10,693	6,547
Depreciation	970	788
Amortization of intangible assets	100	154
Accretion of premium on investment securities	(12)	(30)
Gain on disposal of fixed assets	41
Changes in operating assets and liabilities:
Accounts receivable	14,438	5,682
Deferred commissions	974	361
Other current and noncurrent assets	(656)	(8,125)
Accounts payable	3	1,855
Unearned revenue	3,903	3,455
Customer arrangements with termination rights	(2,360)	12
Accrued expenses and other long-term liabilities	(2,544)	3,398
Net cash provided by operating activities	9,180	724
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(516)	(393)
Proceeds from maturities of investment securities	6,800	24,965
Purchase of investment securities	(2,986)
Net cash provided by investing activities	3,298	24,572
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Employee Stock Purchase Plan	1,069	1,130
Taxes paid for net settlement of stock-settled bonus	(3,724)	(3,024)
Proceeds from exercise of stock options	655	1,817
Net cash used in financing activities	(2,000)	(77)
NET CHANGE IN CASH AND CASH EQUIVALENTS	10,478	25,219
CASH AND CASH EQUIVALENTS-Beginning of period	85,833	54,043
CASH AND CASH EQUIVALENTS-End of period	96,311	79,262
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid for income taxes	474	241
SUPPLEMENTAL DISCLOSURES OF NONCASH FINANCING ACTIVITIES:
Value of shares issued under the Bonus Plans	5,898	5,123
Value of shares issued under the Employee Stock Purchase Plan	2,339	$ 2,110
Unpaid property and equipment purchases	$ 113