Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Available-for-sale securities:
Change in net unrealized gain/loss during the period	$ 8,815	$ (5,463)
Reclassification adjustment for net realized gain on sale of available-for-sale securities included in net income	(94)	(367)
Net unrealized losses	8,721	(5,830)
Employee benefit plans:
Amortization of net retirement plan actuarial gain	320	654
Amortization of net retirement plan prior service cost	14	14
Amortization of net retirement plan transition liability		13
Employee benefit plans	334	681
Other comprehensive (loss) income	9,055	(5,149)
Available-for-sale securities:
Change in net unrealized gain/loss during the period, tax	(3,525)	2,185
Reclassification adjustment for net realized gain on sale of available-for-sale securities included in net income, tax	38	147
Net unrealized losses, tax	(3,487)	2,332
Employee benefit plans:
Amortization of net retirement plan actuarial gain	(128)	(261)
Amortization of net retirement plan prior service cost	(6)	(6)
Amortization of net retirement plan transition liability		(5)
Employee benefit plans, tax	(134)	(272)
Other comprehensive (loss) income, tax	(3,621)	2,060
Available-for-sale securities:
Change in net unrealized gain/loss during the period	5,290	(3,278)
Reclassification adjustment for net realized gain on sale of available-for-sale securities included in net income	(56)	(220)
Net unrealized losses	5,234	(3,498)
Employee benefit plans:
Net retirement plan loss	200	409
Amortization of net retirement plan actuarial gain	192	393
Amortization of net retirement plan prior service cost	8	8
Amortization of net retirement plan transition liability	0	8
Employee benefit plans	200	409
Other comprehensive (loss) income	$ 5,434	$ (3,089)