Schedule I: Condensed Financial Information of Registrant - CONDENSED BALANCE SHEETS (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 83,557	$ 52,255
Total current assets	452,598	259,351
Deferred tax asset	74,412	54,682
Total assets	967,503	763,590
Current liabilities:
Accrued expenses and other current liabilities	121,267	43,949
Total current liabilities	285,011	138,696
Liabilities under tax receivable agreement, net of current portion	75,523	60,297
Other long-term liabilities	3,486	3,848
Commitments and contingencies
Stockholders' equity:
Additional paid-in-capital	252,505	216,141
Accumulated other comprehensive income	1,078	1,718
Retained earnings	68,050	24,403
Total stockholders' equity	396,558	322,445	$ 305,144	$ 293,254
Total liabilities and stockholders' equity	967,503	763,590
Class A Common Stock
Stockholders' equity:
Common stock, value	$ 4	$ 4
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	40,088,000	35,657,000
Common stock, shares outstanding (in shares)	40,088,000	35,657,000
Class B Common Stock
Stockholders' equity:
Common stock, value	$ 1	$ 1
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	10,691,000	14,040,000
Common stock, shares outstanding (in shares)	10,691,000	14,040,000
Parent Company
Current assets:
Cash and cash equivalents	$ 61,943	$ 34,568
Income tax receivable	0	294
Total current assets	61,943	34,862
Intercompany receivable	116,746	117,995
Deferred tax asset	74,464	54,734
Investment in subsidiaries	166,054	97,523
Total assets	419,207	305,114
Current liabilities:
Tax payable	14,684	0
Current portion of liabilities under tax receivable agreement	7,362	2,020
Accrued expenses and other current liabilities	0	40
Total current liabilities	22,046	2,060
Liabilities under tax receivable agreement, net of current portion	75,523	60,297
Other long-term liabilities	0	490
Commitments and contingencies
Stockholders' equity:
Additional paid-in-capital	252,505	216,141
Accumulated other comprehensive income	1,078	1,718
Retained earnings	68,050	24,403
Total stockholders' equity	321,638	242,267
Total liabilities and stockholders' equity	419,207	305,114
Parent Company | Class A Common Stock
Stockholders' equity:
Common stock, value	$ 4	$ 4
Common stock, par value (in dollars per share)	$ 0.0001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	40,088,000	35,657,000
Common stock, shares outstanding (in shares)	40,088,000	35,657,000
Parent Company | Class B Common Stock
Stockholders' equity:
Common stock, value	$ 1	$ 1
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	10,691,000	14,040,000
Common stock, shares outstanding (in shares)	10,691,000	14,040,000