Securities - Trading Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of fair value of trading securities
Trading Securities	$ 368,425	$ 214,146
Investment-related Liabilities
Securities sold, not yet purchased, at fair value	165,704	130,044
U.S. Treasury securities
Schedule of fair value of trading securities
Trading Securities	11,436	20,481
Bonds
Schedule of fair value of trading securities
Trading Securities	75,015	36,244
Residential mortgage-backed securities
Schedule of fair value of trading securities
Trading Securities	55,526	12,505
Commercial mortgage-backed securities
Schedule of fair value of trading securities
Trading Securities	21,717	19,280
Collateralized mortgage obligations
Schedule of fair value of trading securities
Trading Securities	3,150	264
Corporate securities
Schedule of fair value of trading securities
Trading Securities	53,277	34,735
States and political subdivisions
Schedule of fair value of trading securities
Trading Securities	101,655	58,588
Unit investment trusts
Schedule of fair value of trading securities
Trading Securities	37,897	18,400
Private-label securitized product
Schedule of fair value of trading securities
Trading Securities	7,443	12,324
Other
Schedule of fair value of trading securities
Trading Securities	$ 1,309	$ 1,325