Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (12,631)	$ (6,689)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	660	187
Equity-based compensation	2,630	812
Changes in operating assets and liabilities:
Accounts receivable	4,011
Prepaid expenses and other current assets	704	65
Accounts payable	(954)	(87)
Accrued expenses	(1,893)	(134)
Deferred revenue	(4,278)	(778)
Other assets	268	(2,823)
Other long-term liabilities	85	26
Net cash used in operating activities	(11,398)	(9,421)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(4,162)	(1,008)
Net cash used in investing activities	(4,162)	(1,008)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments to acquire in-process research and development		(200)
Payment of preferred unit and preferred stock issuance costs		(100)
Proceeds from options exercised	47
Payment of common stock offering costs		(895)
Net cash provided by (used in) financing activities	47	(1,195)
Net decrease in cash and cash equivalents	(15,513)	(11,624)
Cash and cash equivalents, beginning of period	273,064	75,816
Cash and cash equivalents, end of period	257,551	64,192
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Purchases of property and equipment unpaid at period end	$ 378	918
Acquisition of in-process research and development unpaid at period end		400
Financing costs incurred but unpaid at period end		$ 454