Investments - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Investments [Line Items]
Investments—Affiliates and Other	$ 25,201	$ 10,860
Investments - Consolidated Investment Companies	21,848	22,798
Debt Securities
Schedule of Investments [Line Items]
Investments - Consolidated Investment Companies	13,600	20,900
Stocks of large U.S. and international companies
Schedule of Investments [Line Items]
Investments - Consolidated Investment Companies	5,700	1,600
Separate Accounts
Schedule of Investments [Line Items]
Investments—Affiliates and Other	7,500	6,800
Separate Accounts | Debt Securities
Schedule of Investments [Line Items]
Investments—Affiliates and Other	3,700	3,500
Separate Accounts | Equity
Schedule of Investments [Line Items]
Investments—Affiliates and Other	3,100	2,700
Federated Funds
Schedule of Investments [Line Items]
Investments—Affiliates and Other	$ 17,700	$ 4,100