Investments - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Investment Securities - fair value
Cost	$ 54,170	$ 63,703
Fair Value	56,362	59,271
Sponsored funds
Investment Securities - fair value
Cost	33,082	43,507
Fair Value	33,075	40,191
Equity securities
Investment Securities - fair value
Cost	16,628	16,380
Fair Value	18,827	16,981
Debt securities
Investment Securities - fair value
Cost	4,460	3,816
Fair Value	$ 4,460	$ 2,099