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Stock Based Compensation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock Based Compensation
Shares reserved for future issuance	0		0
Stock Options Granted (in shares)			423
Vesting percentage on each anniversary of the grant date			25.00%
Maximum term for stock options			6 years 3 months	6 years 3 months
Stock based compensation expense	$ (1,601)	$ (1,224)	$ (4,747)	$ (2,678)
Grant date fair value of stock options granted			$ 10.63
Unrecognized compensation cost related to unvested stock options	$ 14,800		$ 14,800
Unrecognized compensation cost related to unvested options, recognized weighted-average period			2 years 9 months 18 days
Class A common stock
Stock Based Compensation
Number of shares reserved	800		800
Class A common stock \| Omnibus Plan
Stock Based Compensation
Shares reserved for future issuance	3,914		3,914
Share available for issuance	1,987		1,987
Maximum
Stock Based Compensation
Maximum term for stock options			10 years