Securities - Trading Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of fair value of trading securities
Trading Securities	$ 676,411	$ 265,534
Investment-related Liabilities
Securities sold, not yet purchased, at fair value	173,509	153,889
US Treasury Securities
Schedule of fair value of trading securities
Trading Securities	200	5,940
Bonds
Schedule of fair value of trading securities
Trading Securities	53,275	36,303
Residential mortgage-backed Securities
Schedule of fair value of trading securities
Trading Securities	407,275	2,539
Commercial mortgage-backed securities
Schedule of fair value of trading securities
Trading Securities	9,599	15,171
Collateralized mortgage obligations
Schedule of fair value of trading securities
Trading Securities	1,098	5,607
Corporate securities
Schedule of fair value of trading securities
Trading Securities	77,435	60,699
States and political subdivisions
Schedule of fair value of trading securities
Trading Securities	90,144	89,946
Unit investment trusts
Schedule of fair value of trading securities
Trading Securities	31,626	41,409
Private-label securitized product
Schedule of fair value of trading securities
Trading Securities	2,398	4,292
Other
Schedule of fair value of trading securities
Trading Securities	$ 3,361	$ 3,628