Other Comprehensive Income (Loss) (Details 2) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Tax benefit		$ 6,967	$ 6,260
Net of tax		14,213	12,713
Amount Reclassified from Accumulated Other Comprehensive (Loss) Income [Member] | Available for Sale Securities [Member]
Net gain on securities transactions	[1]	232	290
Tax benefit	[1]	(93)	(116)
Net of tax	[1]	139	174
Amount Reclassified from Accumulated Other Comprehensive (Loss) Income [Member] | Employee Benefit Plans [Member]
Net retirement plan actuarial loss	[1],[2]	(343)	(731)
Net retirement plan prior service credit	[1],[2]	(30)	179
Amortization, Total before tax	[1]	(373)	(552)
Tax benefit	[1]	149	221
Net of tax	[1]	$ (224)	$ (331)

[1] Amounts in parentheses indicated debits in income statement

[2] The accumulated other comprehensive (loss) income components are included in the computation of net periodic benefit cost (see Note 10 - "Employee Benefit Plan")