Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities
Net loss	$ (22,741)	$ (4,411)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,929	1,869
Gain on disposal of property and equipment	0	(17)
Stock-based compensation	6,265	4,325
Amortization of debt issuance costs	0	83
Interest on end-of-term debt obligation	107	120
Write-down of excess supplies	1,088	0
Noncash lease expense	469	431
Revaluation of acquisition-related contingent consideration	(140)	0
Changes in operating assets and liabilities:
Accounts receivable	4,023	(6,458)
Supplies	(1,323)	(1,702)
Prepaid expenses and other current assets	(664)	(192)
Operating lease liability	(682)	(604)
Other assets	166	25
Accounts payable	122	1,746
Accrued liabilities	(4,343)	1,319
Net cash used in operating activities	(13,724)	(3,466)
Investing activities
Purchases of property and equipment	(1,314)	(1,424)
Proceeds from disposal of property and equipment	0	17
Net cash used in investing activities	(1,314)	(1,407)
Financing activities
Proceeds from the issuance of common stock in a public offering, net of issuance costs	0	137,848
Payment of long-term debt	0	(24,900)
Payment of finance lease liability	0	(152)
Payment of taxes on vested restricted stock units	(2,678)	(676)
Proceeds from the exercise of common stock options and employee stock purchases	5,849	7,405
Net cash provided by financing activities	3,171	119,525
Net (decrease) increase in cash, cash equivalents and restricted cash	(11,867)	114,652
Cash, cash equivalents and restricted cash at beginning of period	159,920	78,598
Cash, cash equivalents and restricted cash at end of period	148,053	193,250
Supplementary cash flow information:
Purchases of property and equipment included in accounts payable and accrued liability	0	72
Interest paid on debt	3	319
Cash and cash equivalents	147,450
Restricted cash	603
Cash, cash equivalents and restricted cash at end of period	$ 148,053	$ 193,250