Business Segment Information - Schedule of Financial Information about Business Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Total revenue	$ 2,125,151	$ 1,919,793	$ 1,991,037
Operations & services	792,509	740,719	721,710
Sales, marketing & client service	174,498	170,959	188,334
Technology services & infrastructure	198,788	189,536	179,904
Strategic initiatives & new business development	205,660	221,150	216,151
Corporate services & other segment expenses	54,307	40,664	41,021
Segment profit (loss)	699,389	556,765	643,917
Investment Managers
Segment Reporting Information [Line Items]
Total revenue	728,390	645,254	599,661
Operations & services	324,602	289,348	270,129
Sales, marketing & client service	40,143	35,914	39,116
Technology services & infrastructure	43,293	42,001	37,867
Strategic initiatives & new business development	33,804	42,811	27,842
Corporate services & other segment expenses	11,243	9,122	7,011
Segment profit (loss)	275,305	226,058	217,696
Private Banks
Segment Reporting Information [Line Items]
Total revenue	541,414	496,317	570,010
Operations & services	200,250	200,946	201,113
Sales, marketing & client service	41,463	37,271	49,449
Technology services & infrastructure	110,154	105,698	102,839
Strategic initiatives & new business development	85,662	86,888	96,484
Corporate services & other segment expenses	22,846	17,687	17,936
Segment profit (loss)	81,039	47,827	102,189
Investment Advisors
Segment Reporting Information [Line Items]
Total revenue	509,408	436,298	447,766
Operations & services	162,396	145,094	137,979
Sales, marketing & client service	31,872	28,547	26,774
Technology services & infrastructure	33,812	31,246	28,247
Strategic initiatives & new business development	48,526	49,657	54,605
Corporate services & other segment expenses	6,296	4,598	4,045
Segment profit (loss)	226,506	177,156	196,116
Institutional Investors
Segment Reporting Information [Line Items]
Total revenue	285,723	289,708	323,353
Operations & services	85,807	87,778	95,860
Sales, marketing & client service	41,612	52,056	50,849
Technology services & infrastructure	5,998	5,284	5,197
Strategic initiatives & new business development	14,241	14,567	15,207
Corporate services & other segment expenses	7,043	5,770	5,139
Segment profit (loss)	131,022	124,253	151,101
Investments in New Businesses
Segment Reporting Information [Line Items]
Total revenue	60,216	52,216	50,247
Operations & services	19,454	17,553	16,629
Sales, marketing & client service	19,408	17,171	22,146
Technology services & infrastructure	5,531	5,307	5,754
Strategic initiatives & new business development	23,427	27,227	22,013
Corporate services & other segment expenses	6,879	3,487	6,890
Segment profit (loss)	$ (14,483)	$ (18,529)	$ (23,185)