Investments - Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Investment Securities - fair value
Cost	$ 69,711	$ 31,999
Fair Value	78,143	39,990
Sponsored funds
Investment Securities - fair value
Cost	59,342	22,378
Fair Value	64,691	25,909
Equity securities
Investment Securities - fair value
Cost	10,362	9,614
Fair Value	13,446	14,078
Debt securities
Investment Securities - fair value
Cost	7	7
Fair Value	$ 6	$ 3