Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flow from operating activities:
Net loss	$ (35,202)	$ (30,180)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	4,223	1,912
Depreciation and amortization	191	23
Net accretion and amortization of investments in marketable securities	(1,703)	0
Change in fair value of common stock warrant liabilities	303	(17)
Change in fair value of contingent consideration	3,000	0
Changes in operating assets and liabilities:
Accounts receivable	(15,500)	0
Prepaid expenses and other current assets	5,270	166
Other assets	(6,580)	2,422
Accounts payable, accrued and other liabilities	(7,096)	891
Operating lease liability	12,767
Deferred revenue	15,500	0
Net cash used in operating activities	(24,827)	(24,783)
Cash flows from investing activities:
Purchases of marketable securities	(145,826)	0
Proceeds from maturities of marketable securities	171,225	0
Purchases of property and equipment	(4,535)	(65)
Net cash provided by (used in) investing activities	20,864	(65)
Cash flows from financing activities:
Payment of contingent consideration	(10,000)	0
Proceeds from issuance of common stock under equity incentive plans	4,379	3,590
Taxes paid related to net share settlement of equity awards	(582)	(292)
Net cash (used in) provided by financing activities	(6,203)	3,298
Net decrease in cash and cash equivalents	(10,166)	(21,550)
Cash and cash equivalents, beginning of the period	68,454	293,503
Cash and cash equivalents, end of the period	58,288	271,953
Noncash financing activities
Purchases of property and equipment in accounts payable and accrued liabilities	$ 5,067	$ 0