Revenue Recognition - Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue Recognition
Total Revenues	$ 263,733	$ 259,410
Investment management fees
Revenue Recognition
Total Revenues	105,219	109,762
Investment management fees - Funds
Revenue Recognition
Total Revenues	102,293	105,745
Investment management fees - Institutional
Revenue Recognition
Total Revenues	2,926	4,017
Underwriting and distribution fees
Revenue Recognition
Total Revenues	136,943	126,245
Unaffiliated
Revenue Recognition
Total Revenues	15,862	17,000
Unaffiliated Rule 12b-1 service and distribution fees
Revenue Recognition
Total Revenues	15,276	16,465
Unaffiliated sales commissions on front-end load mutual fund and variable annuity sales
Revenue Recognition
Total Revenues	451	443
Unaffiliated other revenues
Revenue Recognition
Total Revenues	135	92
Wealth Management
Revenue Recognition
Total Revenues	121,081	109,245
Wealth Management, Fee-based asset allocation product revenues
Revenue Recognition
Total Revenues	77,118	65,230
Wealth Management, Rule 12b-1 service and distribution fees
Revenue Recognition
Total Revenues	14,589	15,405
Wealth Management, sales commissions on front-end load mutual fund and variable annuity sales
Revenue Recognition
Total Revenues	11,958	12,015
Wealth Management, sales commissions on other products
Revenue Recognition
Total Revenues	8,699	7,606
Wealth Management, other revenues
Revenue Recognition
Total Revenues	8,717	8,989
Shareholder service fees
Revenue Recognition
Total Revenues	$ 21,571	$ 23,403