Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Securities available for sale and transferred securities: Before Tax Amount
Change in net unrealized gain/loss during the period, Before Tax Amount	$ 6,763	$ (6,309)	$ 2,360
Reclassification adjustment for net (gains) losses included in net income, Before Tax Amount	(932)	(97)	(2,139)
Net gain (loss) on defined benefit postretirement medical plan realized during the period, Before Tax Amount	(377)	287
Net amortization and deferral on defined benefit postretirement medical plan, Before Tax Amount	35	46
Total other comprehensive income (loss), Before Tax Amount	5,610	(5,736)
Securities available for sale and transferred securities: Tax Expense (Benefit)
Change in net unrealized gain/loss during the period, Tax Expense (Benefit)	2,320	(2,216)
Reclassification adjustment for net (gains) losses included in net income, Tax Expense (Benefit)	(280)	92
Net gain (loss) on defined benefit postretirement medical plan realized during the period, Tax Expense (Benefit)	(132)	101
Net amortization and deferral on defined benefit postretirement medical plan, Tax Expense (Benefit)	12	16
Total other comprehensive income (loss), Tax Expense (Benefit)	2,041	(2,007)
Securities available for sale and transferred securities: Net of Tax Amount
Change in net unrealized gain/loss during the period, Net of Tax Amount	4,443	(4,093)
Reclassification adjustment for net (gains) losses included in net income, Net of Tax Amount	(652)	148
Net gain (loss) on defined benefit postretirement medical plan realized during the period, Net Of Tax	(245)	186
Net amortization and deferral on defined benefit postretirement medical plan, Net of Tax Amount	23	30
Total other comprehensive income (loss), Net of Tax Amount	$ 3,569	$ (3,729)	$ 277