Accumulated Other Comprehensive (Loss) Income - Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized net gain on sale of securities		$ 105	$ 498	$ 2,581	$ 509
Tax (expense) benefit		(1,967)	(838)	(3,870)	(1,997)
Net of tax		11,164	10,457	20,543	18,681
Total before tax		(505)	213	1,444	(5)
Gains and losses on available for sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		105	498	2,581	509
Net Gain (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		(614)	(289)	(1,145)	(521)
Net Prior Service (Cost) Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		4	4	8	7
Reclassification out of accumulated other comprehensive income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period, net of tax		(328)	139	939	(3)
Reclassification out of accumulated other comprehensive income | Gains and losses on available for sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Realized net gain on sale of securities	[1]	105	498	2,581	509
Tax (expense) benefit		(36)	(174)	(903)	(178)
Net of tax		69	324	1,678	331
Reclassification out of accumulated other comprehensive income | Net Gain (Loss)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	[2]	(614)	(289)	(1,145)	(521)
Reclassification out of accumulated other comprehensive income | Net Prior Service (Cost) Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	[2]	4	4	8	7
Reclassification out of accumulated other comprehensive income | Amortization of pension plan items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		(610)	(285)	(1,137)	(514)
Tax benefit		213	100	398	180
Total reclassifications for the period, net of tax		$ (397)	$ (185)	$ (739)	$ (334)

[1] Listed as net gain on sale of securities available for sale on the consolidated statements of income.

[2] These accumulated other comprehensive income components are included in the computation of net periodic pension cost presented in “Note 8 - Employee Benefit Plans.”