CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Class A Common Stock Common stock	Class B Common Stock Common stock	Members' Equity (Deficit)	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Non-controlling Interest	Total
Balance at the beginning of the period at Dec. 31, 2015			$ (92,976)			$ (191)		$ (93,167)
Statement of Stockholders'/Members' Equity
Member distributions prior to IPO			(2,055)					(2,055)
Net income prior to IPO and Reorganization			(8,176)					(8,176)
Other comprehensive income (loss)						(284)		(284)
Equity-based compensation			361					361
Balance at the end of the period at Dec. 31, 2016			(102,846)			(475)		(103,321)
Statement of Stockholders'/Members' Equity
Net income prior to IPO and Reorganization			66,547					66,547
Other comprehensive income (loss)						557		557
Balance at the end of the period at Dec. 31, 2017			(36,299)			82		(36,217)
Statement of Stockholders'/Members' Equity
Member distributions prior to IPO			(26,000)					(26,000)
Net income prior to IPO and Reorganization			13,648					13,648
Effect of IPO and Reorganization	$ 265		$ 48,651	$ 71,196			$ 130,861	250,973
Effect of IPO and Reorganization (shares)	26,450	48,440
Member distribution after IPO							(5,848)	(5,848)
Effect of Follow-on Offering and CW redemptions	$ 112			24,472			(25,293)	(709)
Effect of Follow-on Offering and CW redemptions (in shares)	11,204	(11,204)
Additional paid-in capital related to tax receivable agreement				26,046				26,046
Other comprehensive income (loss)						(902)		(902)
Stock-based compensation				4,704				4,704
Net income after IPO and Reorganization					$ 51,683		84,950	136,633
Balance at the end of the period at Dec. 31, 2018	$ 377			$ 126,418	$ 51,683	$ (820)	$ 184,670	$ 362,328
Balance at the end of the period (shares) at Dec. 31, 2018	37,654	37,236