Investments - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investment Securities - fair value
Cost	$ 49,910	$ 63,703
Fair Value	53,351	59,271
Sponsored funds
Investment Securities - fair value
Cost	33,046	43,507
Fair Value	34,127	40,191
Equity securities
Investment Securities - fair value
Cost	16,842	16,380
Fair Value	19,213	16,981
Debt securities
Investment Securities - fair value
Cost	22	3,816
Fair Value	$ 11	$ 2,099