Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income	$ 19,257	$ 14,535	$ 43,822	$ 41,442
Other comprehensive income, net of tax
Unrealized net holding (losses) gains arising during the period (pre-tax amounts of ($6,927), $1,463, (33,391) and $1,798)	(4,184)	878	(20,167)	1,079
Reclassification adjustment for net gains related to securities available for sale included in net income (pre-tax amounts of $329, $26, $1,413 and $578)	(197)	(16)	(848)	(347)
Pension and other benefits:
Amortization of prior service cost and actuarial gains (pre-tax amounts of $709, $989, $2,244 and $2,702)	426	599	1,354	1,626
Increase in unrecognized actuarial gains (pre-tax amounts of $4,036, $0, $4,036 and $0)	2,421	0	2,421	0
Total other comprehensive (loss) income	(1,534)	1,461	(17,240)	2,358
Comprehensive income	$ 17,723	$ 15,996	$ 26,582	$ 43,800