Condensed Combined Statement of Income for LLCs/LPs Accounted Under Equity Method (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Schedule Of Equity Method Investments [Line Items]
Revenues	$ 20,876	$ 19,281	$ 41,575	$ 38,488
Net income			12,207	9,254
Our share of net income	567	419	1,038	854
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule Of Equity Method Investments [Line Items]
Revenues	2,849	2,497	5,637	5,013
Operating expenses	1,065	1,019	2,172	2,047
Depreciation and amortization	536	447	1,057	889
Interest, net	441	316	872	634
Net income	807	715	1,536	1,443
Our share of net income	$ 567	$ 419	$ 1,038	$ 854