Goodwill and Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill	$ 154,789	$ 147,388
Amortization expense associated with identifiable intangible assets	13,400	3,900	$ 800
Estimated total amortization expense 2021	16,800
Estimated total amortization expense 2022	17,600
Estimated total amortization expense 2023	15,200
Estimated total amortization expense 2024	12,300
Estimated total amortization expense 2025	10,600
Indefinite-lived Intangible Assets [Member]
Goodwill [Line Items]
Goodwill and intangible assets with indefinite lives	154,800	$ 147,400
Muni Brokers L L C [Member]
Goodwill [Line Items]
Goodwill	$ 7,400