Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,415,557	$ 1,390,255
Gross Unrealized Gains	20,146	9,546
Gross Unrealized Losses	3,994	14,117
Fair Value	1,431,709	1,385,684
Obligations of U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	523,478	551,176
Gross Unrealized Gains	12,417	3,512
Gross Unrealized Losses	2	1,795
Fair Value	535,893	552,893
Obligations of U.S. States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	85,443	83,981
Gross Unrealized Gains	1,136	898
Gross Unrealized Losses	58	153
Fair Value	86,521	84,726
Residential Mortgage-Backed Securities U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	136,417	94,459
Gross Unrealized Gains	1,690	1,535
Gross Unrealized Losses	518	1,316
Fair Value	137,589	94,678
Residential Mortgage-Backed Securities U.S. Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	666,575	656,947
Gross Unrealized Gains	4,902	3,599
Gross Unrealized Losses	3,022	10,449
Fair Value	668,455	650,097
Residential Mortgage-Backed Securities Non-U.S. Government Agencies or Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	144	192
Gross Unrealized Gains	1	2
Gross Unrealized Losses	0	0
Fair Value	145	194
U.S. corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,500	2,500
Gross Unrealized Gains	0	0
Gross Unrealized Losses	338	338
Fair Value	2,162	2,162
Total debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,414,557	1,389,255
Gross Unrealized Gains	20,146	9,546
Gross Unrealized Losses	3,938	14,051
Fair Value	1,430,765	1,384,750
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,000	1,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	56	66
Fair Value	$ 944	$ 934