Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income	$ 14,535	$ 15,217	$ 41,442	$ 44,179
Other comprehensive income, net of tax
Unrealized net holding gains arising during the period (pre-tax amounts of $1,463,$5,978, $1,798 and $13,719)	878	3,609	1,079	8,284
Reclassification adjustment for net gains related to securities available for sale included in net income (pre-tax amounts of $26, $12, $578 and $98)	(16)	(7)	(347)	(59)
Pension and other benefits:
Amortization of prior service cost and actuarial gains (pre-tax amounts of $989, $417, $2,702 and $1,248)	599	250	1,626	749
Total other comprehensive income	1,461	3,852	2,358	8,974
Comprehensive income	$ 15,996	$ 19,069	$ 43,800	$ 53,153