Accumulated Other Comprehensive Income (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income, January 1, 2013	$ 29,208
Other Comprehensive Loss Before Reclassifications	(7,763)
Amounts Reclassified from Accumulated Other Comprehensive Income	(1,800)
Net Current-Period Other Comprehensive Loss	(9,563)
Accumulated other comprehensive income, March 31, 2013	19,645
Unrealized Gains and Losses on Net Investment Securities [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income, January 1, 2013	59,777
Other Comprehensive Loss Before Reclassifications	(7,638)
Amounts Reclassified from Accumulated Other Comprehensive Income	(2,003)
Net Current-Period Other Comprehensive Loss	(9,641)
Accumulated other comprehensive income, March 31, 2013	50,136
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income, January 1, 2013	(30,569)
Other Comprehensive Loss Before Reclassifications	(125)
Amounts Reclassified from Accumulated Other Comprehensive Income	203
Net Current-Period Other Comprehensive Loss	78
Accumulated other comprehensive income, March 31, 2013	$ (30,491)