Condensed Combined Statement of Income for LLCs/LPs Accounted Under Equity Method (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Schedule Of Equity Method Investments [Line Items]
Revenues	$ 21,205	$ 19,692	$ 62,780	$ 58,180
Net income			17,551	14,447
Our share of net income	303	517	1,341	1,371
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule Of Equity Method Investments [Line Items]
Revenues	2,736	2,624	8,373	7,637
Operating expenses	1,184	1,047	3,356	3,094
Depreciation and amortization	627	444	1,684	1,333
Interest, net	388	315	1,260	949
Net income	537	818	2,073	2,261
Our share of net income	$ 303	$ 517	$ 1,341	$ 1,371