Consolidated Statements of Changes in Stockholders' Deficit - USD ($) $ in Thousands		Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Total
Balance at Dec. 31, 2017	[1]	$ 0	$ (26,495)	$ 0	$ (26,495)
Balance (in shares) at Dec. 31, 2017	[1]	5,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of stock split		$ 15	(15)	0	0
Effect of stock split (in shares)		15,072,647
Common Stock issued to performance unit plan participants		$ 5	19,118	0	19,123
Common Stock issued to performance unit plan participants (in shares)		4,922,353
Reclassification of warrant liability to equity		$ 0	12,952	0	12,952
Cash received for warrant exercise		0	116	0	116
Common Stock issued upon initial public offering		$ 5	68,709	0	68,714
Common Stock issued upon initial public offering (in shares)		4,925,727
Issuance costs of initial public offering		$ 0	(5,232)	0	(5,232)
Issuance costs of initial public offering (in shares)		0
Share-based compensation		$ 0	2,278	0	2,278
Share-based compensation (in shares)		31,582
Net loss		$ 0	0	(61,376)	(61,376)
Balance at Dec. 31, 2018		$ 25	71,431	(61,376)	10,080
Balance (in shares) at Dec. 31, 2018		24,957,309
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2014-09, ASU 2018-07 | ASU 2014-09 and ASU 2018-07 [Member]		$ 0	20	(2,852)	(2,832)
Common Stock issued upon initial public offering		$ 8	37,827	0	37,835
Common Stock issued upon initial public offering (in shares)		8,050,000
Fair value of warrants issued		$ 0	6,800	0	6,800
Common Stock issued upon warrant exercises		$ 1	1,820	0	1,821
Common Stock issued upon warrant exercises (in shares)		428,571
Costs of public equity offering		$ 0	(540)	0	(540)
Shares issued under employee stock purchase plan		$ 0	237	0	237
Shares issued under employee stock purchase plan (in shares)		56,378
Share-based compensation		$ 0	6,723	0	6,723
Share-based compensation (in shares)		70,627
Net loss		$ 0	0	(66,246)	(66,246)
Balance at Dec. 31, 2019		$ 34	$ 124,318	$ (130,474)	$ (6,122)
Balance (in shares) at Dec. 31, 2019		33,562,885

[1] Represents balances as of December 31, 2017 as adjusted for the reorganization from LLC to C corporation business structure effective as of the close of business on that date.