Investments - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Investments—Affiliates and Other	$ 43,209	$ 26,935
Investments - consolidated investment companies	71,103	64,526
Debt Securities
Schedule of Investments [Line Items]
Investments - consolidated investment companies	38,000	38,900
Stocks of large U.S. and international companies
Schedule of Investments [Line Items]
Investments - consolidated investment companies	26,800	22,600
Federated Hermes Funds
Schedule of Investments [Line Items]
Investments—Affiliates and Other	33,800	20,100
Separate Accounts
Schedule of Investments [Line Items]
Investments—Affiliates and Other	9,400	6,800
Separate Accounts | Debt Securities
Schedule of Investments [Line Items]
Investments—Affiliates and Other	5,500	2,600
Separate Accounts | Equity
Schedule of Investments [Line Items]
Investments—Affiliates and Other	$ 3,000	$ 3,000