Investments - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cost	$ 55,882	$ 63,703
Fair Value	60,990	59,271
Sponsored funds
Debt Securities, Available-for-sale [Line Items]
Cost	44,588	43,507
Fair Value	47,654	40,191
Equity securities
Debt Securities, Available-for-sale [Line Items]
Cost	11,250	16,380
Fair Value	13,320	16,981
Debt securities
Debt Securities, Available-for-sale [Line Items]
Cost	44	3,816
Fair Value	$ 16	$ 2,099