Intangible Assets Intangible Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Renewable investment advisory contracts [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	$ 73,900	$ 70,400
Trade Names [Member]
Indefinite-lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets	1,900	1,900
Customer Relationships [Member]
Indefinite-lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net	$ 1,100	$ 1,700