CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
STATEMENTS OF COMPREHENSIVE INCOME
Defined benefit plan adjustments, tax	$ (1,395)	$ 2,933	$ 1,273
Amortization and reversal of net unrealized loss on securities transferred from available-for-sale to held-to-maturity, taxes	(91)	(201)	(83)
Reduction in non-credit component of otti charge, taxes	(137)	(585)	(1,130)
Non-credit component of OTTI charge recognized during the period, tax	3	11	127
Reclassification adjustment for securities sold during the period, taxes	461	14	384
Net unrealized securities gains arising during the period, tax	$ 1,983	$ 615	$ 474