Revenue Recognition - Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue Recognition
Total Revenues	$ 259,410	$ 297,615
Investment management fees
Revenue Recognition
Total Revenues	109,762	133,692
Investment management fees - Funds
Revenue Recognition
Total Revenues	105,745	127,663
Investment management fees - Institutional
Revenue Recognition
Total Revenues	4,017	6,029
Underwriting and distribution fees
Revenue Recognition
Total Revenues	126,245	138,041
Unaffiliated
Revenue Recognition
Total Revenues	16,712	21,631
Unaffiliated Rule 12b-1 service and distribution fees
Revenue Recognition
Total Revenues	16,182	20,976
Unaffiliated sales commissions on front-end load mutual fund and variable annuity sales
Revenue Recognition
Total Revenues	438	470
Unaffiliated other revenues
Revenue Recognition
Total Revenues	92	185
Broker-Dealer
Revenue Recognition
Total Revenues	109,533	116,410
Broker-Dealer, Fee-based asset allocation product revenues
Revenue Recognition
Total Revenues	65,230	65,516
Broker-Dealer, Rule 12b-1 service and distribution fees
Revenue Recognition
Total Revenues	15,688	18,377
Broker-Dealer, sales commissions on front-end load mutual fund and variable annuity sales
Revenue Recognition
Total Revenues	12,020	14,427
Broker-Dealer, sales commissions on other products
Revenue Recognition
Total Revenues	7,606	8,422
Broker-Dealer, other revenues
Revenue Recognition
Total Revenues	8,989	9,668
Shareholder service fees
Revenue Recognition
Total Revenues	$ 23,403	$ 25,882