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Stock Incentive Plan - Narrative (Details) - USD ($)		12 Months Ended
	Apr. 03, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Subsidiary, Sale of Stock [Line Items]
Value of shares withheld for taxes		$ 1,985,000	$ 1,109,000	$ 452,000
Stock issued during period (in shares)		110,000
Warrants exercised (in shares)		470,000
Stock issued related to warrants exercised		$ 1,477,000	$ 0	$ 0
RSAs
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 653,000
Share vesting period		3 years
Grants in the period (in shares)		51,000	52,000	49,000
Grants in the period (USD per share)		$ 8.73	$ 12.06	$ 11.64
Fair value of shares vested in period		$ 799,000	$ 1,261,000	$ 1,107,000
Vested (in shares)		71,000
Vested (in usd per share)		$ 11.22
Shares withheld for taxes (in shares)		11,000	17,000	28,000
Value of shares withheld for taxes		$ 140,000	$ 255,000	$ 361,000
RSUs
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 2,614,000
Share vesting period		3 years
Grants in the period (in shares)		169,000	261,000	248,000
Grants in the period (USD per share)		$ 13.52	$ 12.14	$ 16.08
Fair value of shares vested in period		$ 2,918,000	$ 1,709,000	$ 392,000
Vested (in shares)		213,000
Vested (in usd per share)		$ 13.72
PSUs
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 8,305,000
Share vesting period		3 years
Grants in the period (in shares)		176,000	310,000	890,000
Grants in the period (USD per share)		$ 14.06	$ 11.81	$ 11.64
Fair value of shares vested in period		$ 1,620,000	$ 948,000
Vested (in shares)		133,000		0
Vested (in usd per share)		$ 12.20
RSUs and PSUs
Subsidiary, Sale of Stock [Line Items]
Shares withheld for taxes (in shares)		123,000	74,000	8,000
Value of shares withheld for taxes		$ 1,845,000	$ 964,000	$ 92,000
Warrants to the Lenders Under the Loan Agreement | Loan and Security Agreement
Subsidiary, Sale of Stock [Line Items]
Warrants, term	5 years
Number of warrants (in shares)	1,000,000
Warrant exercise price (USD per share)	$ 10.25
Stock Incentive Plan & ESPP
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 11,643,000	3,788,000	$ 3,064,000
Stock Incentive Plan
Subsidiary, Sale of Stock [Line Items]
Number of shares authorized to issue (in shares)				1,800,000
Number of shares available for grant (in shares)		0
Unrecognized compensation cost		$ 10,800,000
Weighted-average recognition period		2 years 3 months 18 days
Stock Incentive Plan | RSAs, RSUs and PSUs
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 11,572,000	3,761,000	$ 3,064,000
ESPP
Subsidiary, Sale of Stock [Line Items]
Number of shares available for grant (in shares)		748,000
ESPP | Employee Stock
Subsidiary, Sale of Stock [Line Items]
Total compensation cost attributable to shares awarded		$ 71,000	$ 27,000
Maximum annual contribution per employee		15.00%
Maximum annual contribution amount		$ 25,000
Purchase price of common stock percent		85.00%

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