CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (87,441)	$ (61,447)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	4,457	537
Stock-based compensation expense	9,676	10,392
Change in fair value of contingent consideration	734	866
Goodwill impairment charge	18,504
Changes in operating assets and liabilities:
Accounts receivable	(14,509)	(1,701)
Inventory	606	(1,026)
Prepaid expenses and other assets	1,973	2,345
Accounts payable	(583)	4,693
Accrued expenses	13,887	1,636
Net cash used in operating activities	(52,696)	(43,705)
Cash flows from investing activities:
Purchases of property and equipment	(525)	(650)
Purchases of marketable securities	(89,407)	(74,246)
Proceeds from sales and maturities of marketable securities	117,500	144,375
Net cash provided by investing activities	27,568	69,479
Cash flows from financing activities:
Finance lease payments	(240)	(335)
Proceeds from the exercise of employee stock options	3	394
Net cash (used in) provided by financing activities	(237)	59
Net increase (decrease) in cash and cash equivalents	(25,365)	25,833
Cash and cash equivalents at beginning of period	57,019	20,202
Cash and cash equivalents at end of period	31,654	46,035
Supplemental disclosure of non-cash investing and financing activities:
Additions to property and equipment included in accounts payable	$ 392	442
Property and equipment obtained pursuant to capital lease financing arrangements		1,896
Offering costs included in accounts payable		$ 20