Consolidated Statements of Comprehensive Income (unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net income	$ 7,649	$ 13,650
Other comprehensive (loss) income, net of tax
Unrealized net holding (losses) gains arising during the period (pre-tax amounts of ($1,752) and $644)	(1,058)	386
Reclassification adjustment for net gains related to securities available-for-sale included in net income (pre-tax amounts of $1,145 and $455)	(691)	(273)
Pension and other benefits:
Amortization of prior service cost and actuarial gains (pre-tax amounts of $826 and $857)	503	516
Total other comprehensive income	(1,246)	629
Comprehensive income	$ 6,403	$ 14,279