Schedule of Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Change in net unrealized Gain during period:
Change in net unrealized gain during period, before tax amount	$ 10,608	$ 14,351
Change in net unrealized gain during period, tax expense (benefit)	4,174	5,647
Change in net unrealized gain during period, net of tax amount	6,434	8,704
Reclassification adjustment for gains included in net income:
Reclassification adjustment for gains included in net income, before tax amount	(6)	(71)
Reclassification adjustment for gains included in net income, tax expense (benefit)	(2)	(28)
Reclassification adjustment for gains included in net income, net of tax amount	(4)	(43)
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity	451	0
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Tax	177	0
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity	274	0
Change in net actuarial loss:
Change in net actuarial loss, before tax amount	15	35
Change in net actuarial loss, tax expense (benefit)	6	14
Change in net actuarial loss, net of tax amount	9	21
Other comprehensive income (loss):
Other comprehensive income (loss), before tax	11,068	14,315
Total other comprehensive income, tax expense (benefit)	4,355	5,633
Total other comprehensive income, net of tax amount	$ 6,713	$ 8,682