Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other comprehensive (loss) income, before tax
Unrealized net holding (losses) gains arising during the period, pre-tax amounts	$ 18,069	$ (41,059)	$ (2,471)
Reclassification adjustment for net gains related to securities available for sale included in net income, pre-tax amounts	92	1,426	599
Amortization of unrealized net gains and losses related to the reclassification of available for sale investment securities to held to maturity, pre-tax amounts	(421)	0	0
Amortization of prior service cost and actuarial gains, pre-tax amounts	75	2,790	3,593
Decrease (Increase) in prior service costs and unrecognized actuarial loss, pre-tax amounts	$ (19,245)	$ 21,923	$ (24)