Reclassification Adjustments Out of Other Comprehensive (Loss) Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains (losses)	$ 14	$ (61)	$ 21	$ 1,084
Salaries and employee benefits	31,142	29,160	60,676	56,207
Tax benefit	14,059	7,424	22,731	10,781
Net Income	27,640	16,916	45,649	24,565
Total reclassification during the period, net of tax	3	463	10	272
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains (losses)	(14)	61	(21)	(1,084)
Tax benefit	6	(24)	8	434
Net Income	(8)	37	(13)	(650)
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits			(110)	(111)
Tax benefit	8	284	15	614
Net Income	11	426	23	922
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of net gains [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	74	765
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of prior service costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	$ (55)	$ (55)	$ 148	$ 1,647