Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		9 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018
Cash flow from operating activities:
Net loss	$ (37,763)	$ (35,202)	$ (29,037)	$ (30,180)	$ (72,965)	$ (59,217)	$ (72,965)
Adjustments to reconcile net loss from continuing operations to net cash used in operating activities:
Stock-based compensation					9,581	4,971
Depreciation and amortization					552	50
Net accretion and amortization of investments in marketable securities					(3,299)	0
Change in fair value of warrant liabilities					158	31
Change in fair value of contingent purchase consideration	(700)		(2,500)		2,300	(2,500)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets					6,071	(3,482)
Other assets					(5,963)	2,891
Accounts payable, accrued and other liabilities					(5,193)	1,689
Operating lease liability					12,588
Deferred revenue					14,431	0
Net cash used in operating activities					(41,739)	(55,567)
Cash flows from investing activities:
Purchases of marketable securities					(251,782)	0
Proceeds from maturities of marketable securities					289,357	0
Purchases of property and equipment					(8,922)	(84)
Net cash provided by (used in) investing activities					28,653	(84)
Cash flows from financing activities:
Payment of contingent consideration					(10,000)	0
Proceeds from issuance of common stock under equity incentive plans					6,026	5,427
Taxes paid related to net share settlement of equity awards					(606)	(1,426)
Proceeds from issuance of common stock, net of issuance costs					0	30,250
Net cash (used in) provided by financing activities					(4,580)	34,251
Net decrease in cash and cash equivalents					(17,666)	(21,400)
Cash and cash equivalents, beginning of the period		$ 68,454		$ 293,503	68,454	293,503	$ 293,503
Cash and cash equivalents, end of the period	$ 50,788		$ 272,103		50,788	272,103
Noncash financing activities:
Purchases of property and equipment in accounts payable and accrued liabilities					$ 662	$ 0