Revenue Recognition - Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue Recognition
Total Revenues	$ 270,680	$ 295,118	$ 800,244	$ 888,071
Investment management fees
Revenue Recognition
Total Revenues	111,806	129,302	334,438	393,385
Investment management fees - Funds
Revenue Recognition
Total Revenues	107,926	123,764	322,678	376,193
Investment management fees - Institutional
Revenue Recognition
Total Revenues	3,880	5,538	11,760	17,192
Underwriting and distribution fees
Revenue Recognition
Total Revenues	135,787	140,308	395,527	416,222
Unaffiliated
Revenue Recognition
Total Revenues	16,431	20,274	50,043	62,611
Unaffiliated Rule 12b-1 service and distribution fees
Revenue Recognition
Total Revenues	16,003	19,707	48,514	60,734
Unaffiliated sales commissions on front-end load mutual fund and variable annuity sales
Revenue Recognition
Total Revenues	361	441	1,287	1,418
Unaffiliated other revenues
Revenue Recognition
Total Revenues	67	126	242	459
Wealth Management
Revenue Recognition
Total Revenues	119,356	120,034	345,484	353,611
Wealth Management, Fee-based asset allocation product revenues
Revenue Recognition
Total Revenues	73,356	69,468	208,806	201,565
Wealth Management, Rule 12b-1 service and distribution fees
Revenue Recognition
Total Revenues	16,426	18,106	48,441	54,591
Wealth Management, sales commissions on front-end load mutual fund and variable annuity sales
Revenue Recognition
Total Revenues	12,523	13,651	36,845	41,900
Wealth Management, sales commissions on other products
Revenue Recognition
Total Revenues	8,024	9,111	24,127	26,632
Wealth Management, other revenues
Revenue Recognition
Total Revenues	9,027	9,698	27,265	28,923
Shareholder service fees
Revenue Recognition
Total Revenues	$ 23,087	$ 25,508	$ 70,279	$ 78,464