Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 7,995	$ (689)
Available-for-sale investment securities:
Gross unrealized holding gain arising in the period	12,329	8,886
Related tax expense	(4,316)	(3,111)
Less: reclassification adjustment for net gain included in net income	96	600
Related tax expense	(34)	(210)
Net effect on other comprehensive income	7,951	5,385
Defined benefit plans:
Net loss arising during the period	0	(26)
Related tax benefit	0	9
Amortization of unrecognized loss and service cost on benefit plans	0	32
Related tax expense	0	(12)
Recognition of loss due to settlement and curtailment	0	269
Related tax expense	0	(94)
Net effect on other comprehensive income	0	178
Total other comprehensive income, net of tax expense	7,951	5,563
Total comprehensive income	$ 15,946	$ 4,874