Stockholders' Equity - Other (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) item $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Stockholders' Equity
Shares available for issuance	1,100
Stock option and restricted stock
Stock-based compensation
Stock-based compensation expense (in dollars) | $	$ 5,300	$ 4,800
Stock options
Stock-based compensation
Unrecognized compensation cost related to unvested stock options (in dollars) | $	$ 2,600
Weighted-average periods over which unrecognized compensation cost recognized	1 year 4 months 24 days
Estimated forfeitures (as a percent)	1.50%
Valuation assumptions
Dividend yield (as a percent)	0.00%
Number of shares
Outstanding at the beginning of the period (in shares)	3,855	2,910
Granted (in shares)	80	1,025
Exercised (in shares)		(60)
Expired (in shares)		(20)
Outstanding at the end of the period (in shares)	3,935	3,855	2,910
Vested at the end of the period (in shares)	3,140
Exercisable at the end of the period (in shares)	3,140
Weighted-average exercise price
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 11.72	$ 11.62
Granted (in dollars per share) | $ / shares	10.05	12.06
Exercised (in dollars per share) | $ / shares		11.63
Expired (in dollars per share) | $ / shares		13.64
Outstanding at the end of the period (in dollars per share) | $ / shares	11.69	$ 11.72	$ 11.62
Vested at the end of the period (in dollars per share) | $ / shares	11.64
Exercisable at the end of the period (in dollars per share) | $ / shares	$ 11.64
Weighted-average remaining contractual term
Outstanding	5 years 1 month 6 days	6 years 1 month 6 days	5 years 7 months 6 days
Granted	6 years	6 years
Vested at the end of the period	4 years 2 months 12 days
Exercisable at the end of the period	4 years 2 months 12 days
Aggregate intrinsic value
Outstanding at the beginning of the period (in dollars) | $	$ 12,101	$ 2,806
Outstanding at the end of the period (in dollars) | $	291	$ 12,101	$ 2,806
Vested at the end of the period (in dollars) | $	264
Exercisable at the end of the period (in dollars) | $	$ 264
Weighted-average grant date fair value of options granted (in dollars per share) | $ / shares	$ 4.01	$ 4.93
Restricted Stock
Stock-based compensation
Unrecognized compensation cost related to unvested restricted stock (in dollars) | $	$ 3,500
Weighted-average periods over which unrecognized compensation cost recognized	1 year 4 months 24 days
Number of shares
Outstanding at the beginning of the period (in shares)	592	370
Granted (in shares)	163	581
Vested (in shares)	(256)	(352)
Forfeited (in shares)		(7)
Outstanding at the end of the period (in shares)	499	592	370
Weighted-average grant date fair value
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 12.32	$ 9.86
Granted (in dollars per share) | $ / shares	9.59	12.37
Vested (in dollars per share) | $ / shares	12.65	9.78
Forfeited (in dollars per share) | $ / shares		14.55
Outstanding at the end of the period (in dollars per share) | $ / shares	$ 11.26	$ 12.32	$ 9.86
Time Based Restricted Stock Awards and Stock Option
Stockholders' Equity
Number of equal annual installments for vesting of awards | item	3
Time Based Stock Option | Black Scholes Pricing Model
Valuation assumptions
Risk-free interest rate (as a percent)		1.60%
Volatility (as a percent)		40.30%
Weighted-average expected term (years)	6 years	6 years
Time Based Stock Option | Minimum | Black Scholes Pricing Model
Valuation assumptions
Risk-free interest rate (as a percent)	0.42%
Volatility (as a percent)	44.20%
Time Based Stock Option | Maximum | Black Scholes Pricing Model
Valuation assumptions
Risk-free interest rate (as a percent)	0.50%
Volatility (as a percent)	46.10%
Time Based Restricted Stock
Aggregate intrinsic value
Vesting period	3 years
Common Class A
Stockholders' Equity
Shares authorized for issuance	7,200