Securities (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 666,429	$ 723,785
Less Than 12 Months, Unrealized Losses	15,972	27,050
12 Months Or Longer, Fair Value	148,922	101,938
12 Months Or Longer, Unrealized Losses	7,662	6,477
Total Fair Value	815,351	825,723
Total Unrealized Losses	23,634	33,527
Obligations of U.S. Government sponsored entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	279,989	337,967
Less Than 12 Months, Unrealized Losses	4,557	9,467
12 Months Or Longer, Fair Value	3,227	1,761
12 Months Or Longer, Unrealized Losses	48	38
Total Fair Value	283,216	339,728
Total Unrealized Losses	4,605	9,505
Obligations of U.S. states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	18,004	21,821
Less Than 12 Months, Unrealized Losses	373	821
12 Months Or Longer, Fair Value	8,275	6,173
12 Months Or Longer, Unrealized Losses	476	626
Total Fair Value	26,279	27,994
Total Unrealized Losses	849	1,447
Residential Mortgage-backed securities U.S. Government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	64,054	70,052
Less Than 12 Months, Unrealized Losses	1,552	2,701
12 Months Or Longer, Fair Value	12,670	14,874
12 Months Or Longer, Unrealized Losses	692	941
Total Fair Value	76,724	84,926
Total Unrealized Losses	2,244	3,642
Residential Mortgage-backed securities U.S. Government sponsored entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	304,382	293,945
Less Than 12 Months, Unrealized Losses	9,490	14,061
12 Months Or Longer, Fair Value	121,686	76,070
12 Months Or Longer, Unrealized Losses	6,010	4,432
Total Fair Value	426,068	370,015
Total Unrealized Losses	15,500	18,493
U.S. corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	0	0
Less Than 12 Months, Unrealized Losses	0	0
12 Months Or Longer, Fair Value	2,125	2,125
12 Months Or Longer, Unrealized Losses	375	375
Total Fair Value	2,125	2,125
Total Unrealized Losses	375	375
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	0	0
Less Than 12 Months, Unrealized Losses	0	0
12 Months Or Longer, Fair Value	939	935
12 Months Or Longer, Unrealized Losses	61	65
Total Fair Value	939	935
Total Unrealized Losses	$ 61	$ 65