Schedule of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Change in net unrealized Gain during period:
Change in net unrealized gain during period, before tax amount	$ 8,006	$ 10,043	$ 17,365	$ 18,671
Change in net unrealized gain during period, tax expense (benefit)	3,298	3,947	6,985	7,322
Change in net unrealized gain during period, net of tax amount	4,708	6,096	10,380	11,349
Reclassification adjustment for gains included in net income:
Reclassification adjustment for gains included in net income, before tax amount	(5)	(108)	(7)	(87)
Reclassification adjustment for gains included in net income, tax expense (benefit)	(2)	(42)	(3)	(34)
Reclassification adjustment for gains included in net income, net of tax amount	(3)	(66)	(4)	(53)
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity	464	452	929	904
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Tax	191	170	374	340
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity	273	282	555	564
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	(486)	(804)	(437)	(3,002)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	(201)	(305)	(176)	(1,141)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(285)	(499)	(261)	(1,861)
Change in net actuarial loss:
Change in net actuarial loss, before tax amount	(176)	13	(914)	28
Change in net actuarial loss, tax expense (benefit)	(72)	5	(368)	11
Change in net actuarial loss, net of tax amount	(104)	8	(546)	17
Other comprehensive income (loss):
Other comprehensive income (loss), before tax	7,803	9,596	16,936	16,514
Total other comprehensive income, tax expense (benefit)	3,214	3,775	6,812	6,498
Total other comprehensive income, net of tax amount	$ 4,589	$ 5,821	$ 10,124	$ 10,016