Investment Securities - Available for sale sponsored funds with fair values below carrying values (Details) - Sponsored funds - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair value
Less than 12 months	$ 56,153	$ 71,051
12 months or longer	35,291	34,182
Total temporarily impaired securities	91,444	105,233
Unrealized losses
Less than 12 months	(1,268)	(1,834)
12 months or longer	(4,188)	(5,615)
Total Unrealized losses on temporarily impaired securities	$ (5,456)	$ (7,449)