Stockholders' Equity - Capital Stock (Details) $ / shares in Units, $ in Thousands		12 Months Ended		30 Months Ended
	Dec. 31, 2019 item shares	Dec. 31, 2019 USD ($) item shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2019 USD ($) item shares	Aug. 15, 2018 USD ($)	Jun. 20, 2017 USD ($) $ / shares
Capital Stock
Amount of stock repurchased | $		$ 662	$ 2,443
Common Class B
Capital Stock
Common stock, shares issued	19,720,381	19,720,381	19,720,381	19,720,381
Common stock, shares outstanding	19,720,381	19,720,381		19,720,381
Number of votes per share of common stock | item	10	10		10
Common Class A
Capital Stock
Common stock, shares issued excluding treasury shares	20,184,412	20,184,412		20,184,412
Common stock, shares issued	25,202,314	25,202,314	24,849,589	25,202,314
Common stock, shares outstanding	20,184,412	20,184,412		20,184,412
Authorized share repurchase amount	0	0		0
Stock repurchase price (in dollars per share) | $ / shares						$ 0.0001
Number of votes per share of common stock | item	1	1		1
Common Class A | Treasury Stock
Capital Stock
Number of shares repurchased	2,000,000	51,227
Amount of stock repurchased | $		$ 662	$ 2,443	$ 25,000
Common Class A | Maximum
Capital Stock
Authorized repurchase amount | $					$ 25,000	$ 25,000