Revenue Recognition - Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue Recognition
Total Revenues	$ 295,351	$ 263,733
Investment management fees
Revenue Recognition
Total Revenues	118,016	105,219
Funds
Revenue Recognition
Total Revenues	114,395	102,293
Institutional
Revenue Recognition
Total Revenues	3,621	2,926
Underwriting and distribution fees
Revenue Recognition
Total Revenues	154,795	136,943
Unaffiliated
Revenue Recognition
Total Revenues	14,701	15,862
Unaffiliated service and distribution fees
Revenue Recognition
Total Revenues	14,642	15,276
Unaffiliated sales commissions
Revenue Recognition
Total Revenues	15	451
Unaffiliated Other revenues
Revenue Recognition
Total Revenues	44	135
Wealth Management
Revenue Recognition
Total Revenues	140,094	121,081
Wealth Management Advisory Fees
Revenue Recognition
Total Revenues	94,280	77,118
Wealth Management Service and distribution fees
Revenue Recognition
Total Revenues	16,763	14,589
Wealth Management Sales commissions
Revenue Recognition
Total Revenues	19,423	20,657
Wealth Management Other revenues
Revenue Recognition
Total Revenues	9,628	8,717
Shareholder service fees
Revenue Recognition
Total Revenues	$ 22,540	$ 21,571