Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 20,020	$ 46,856	$ 49,822
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	26,691	22,323	20,678
Impairment charge - leased assets	7,902	0	0
Bad debt expense	2,903	4,964	2,257
Equity-based compensation expense	16,267	10,934	9,176
Deferred income tax expense	1,840	2,310	9,511
Fair value adjustments to contingent consideration	814	241	(1,289)
Non-cash change in tax receivable agreements liability	0	0	(6,145)
Non-cash lease expense (benefit)	(508)	0	0
Other, net	1,051	1,252	988
Changes in operating assets and liabilities
Accounts and notes receivable, current portion	(3,460)	(5,614)	(3,241)
Advances from/to affiliates	0	0	581
Other current and noncurrent assets	(10,665)	(6,084)	2,170
Other current and noncurrent liabilities	9,035	6,737	(3,466)
Payments pursuant to tax receivable agreements	(3,562)	(3,556)	(6,305)
Income taxes receivable/payable	2,109	178	1,099
Deferred revenue, current and noncurrent	410	(1,566)	228
Net cash provided by operating activities	70,847	78,975	76,064
Cash flows from investing activities:
Purchases of property, equipment and capitalization of software	(6,903)	(13,226)	(7,787)
Acquisitions, net of cash acquired of $867k, $55k and $362k, respectively	(10,627)	(14,945)	(25,888)
Restricted cash acquired with the Marketing Funds acquisition	0	28,495	0
Other	0	(1,200)	0
Net cash used in investing activities	(17,530)	(876)	(33,675)
Cash flows from financing activities:
Payments on debt	(2,634)	(2,622)	(3,171)
Distributions paid to non-controlling unitholders	(14,058)	(15,430)	(14,559)
Dividends and dividend equivalents paid to Class A common stockholders	(16,354)	(15,074)	(14,306)
Payments related to tax withholding for share-based compensation	(2,544)	(1,110)	(895)
Payment of contingent consideration	(409)	(306)	(221)
Net cash used in financing activities	(35,999)	(34,542)	(33,152)
Effect of exchange rate changes on cash	308	70	(70)
Net increase in cash, cash equivalents and restricted cash	17,626	43,627	9,167
Cash, cash equivalents and restricted cash, beginning of year	103,601	59,974	50,807
Cash, cash equivalents and restricted cash, end of period	121,227	103,601	59,974
Supplemental disclosures of cash flow information:
Cash paid for interest	8,663	11,690	11,525
Net cash paid for income taxes	4,993	8,429	5,769
Schedule of non-cash investing activities:
Class A shares issued as consideration for acquisitions	8,800	0	0
Increase (decrease) in accounts payable and accrued liabilities for purchases of property, equipment and capitalization of software	$ 1,419	$ (94)	$ 1,080