Consolidated Statements of Comprehensive Income (unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other comprehensive income, net of tax:
Unrealized net holding gains (losses) arising during the period , pre-tax amounts	$ 1,355	$ (2,931)	$ 4,719	$ 14,010
Reclassification adjustment for net losses (gains) related to securities available for sale included in net income, pre-tax amounts	(4)	0	(2)	30
Reclassification adjustment for an impairment write-down of equity security, pre-tax amounts	0	0	1,312	0
Unrealized (loss) gain on derivatives (cash flow hedges), pre-tax amounts	(63)	782	(167)	719
Amortization of unrealized net gains related to the reclassification of available for sale investment securities to held to maturity, pre-tax amounts	212	267	675	843
Amortization of prior service cost and actuarial loss, pre-tax amounts	$ 480	$ 519	$ 1,350	$ 1,544