Schedule of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Change in net unrealized Gain during period:
Change in net unrealized gain during period, before tax amount	$ 9,354	$ 8,613
Change in net unrealized gain during period, tax expense (benefit)	3,681	3,360
Change in net unrealized gain during period, net of tax amount	5,673	5,253
Reclassification adjustment for gains included in net income:
Reclassification adjustment for gains included in net income, before tax amount	(2)	21
Reclassification adjustment for gains included in net income, tax expense (benefit)	(1)	8
Reclassification adjustment for gains included in net income, net of tax amount	(1)	13
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity	463	465
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Tax	182	183
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity	281	282
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	49	(2,197)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	19	(835)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	30	(1,362)
Change in net actuarial loss:
Change in net actuarial loss, before tax amount	(739)	15
Change in net actuarial loss, tax expense (benefit)	(291)	6
Change in net actuarial loss, net of tax amount	(448)	9
Other comprehensive income (loss):
Other comprehensive income (loss), before tax	9,125	6,917
Total other comprehensive income, tax expense (benefit)	3,590	2,722
Total other comprehensive income, net of tax amount	$ 5,535	$ 4,195