Goodwill and Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Goodwill and identifiable intangible assets
Goodwill	$ 106,970	$ 106,970
Other	200	200
Total identifiable intangible assets	38,899	40,099
Total goodwill and identifiable intangible assets	145,869	147,069
Mutual fund management advisory contracts
Goodwill and identifiable intangible assets
Mutual fund contracts	$ 38,699	38,699
Mutual fund management subadvisory contract
Goodwill and identifiable intangible assets
Mutual fund contracts		$ 1,200