Investment Securities - Available for sale sponsored funds with fair values below carrying values (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair value
Less than 12 months	$ 62,651
12 months or longer	35,900
Total temporarily impaired securities	98,551
Unrealized losses
Less than 12 months	(1,211)
12 months or longer	(3,581)
Total Unrealized losses on temporarily impaired securities	(4,792)
Cerficates of deposit
Fair value
Less than 12 months	4,999
Total temporarily impaired securities	4,999
Unrealized losses
Less than 12 months	(1)
Total Unrealized losses on temporarily impaired securities	(1)
Corporate bonds
Fair value
Less than 12 months	24,146
Total temporarily impaired securities	24,146
Unrealized losses
Less than 12 months	(20)
Total Unrealized losses on temporarily impaired securities	(20)
Sponsored funds
Fair value
Less than 12 months	33,506	$ 71,051
12 months or longer	35,900	34,182
Total temporarily impaired securities	69,406	105,233
Unrealized losses
Less than 12 months	(1,190)	(1,834)
12 months or longer	(3,581)	(5,615)
Total Unrealized losses on temporarily impaired securities	$ (4,771)	$ (7,449)