Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income	$ 13,257	$ 14,655	$ 26,907	$ 28,962
Other comprehensive income, net of tax
Unrealized net holding (losses) gains arising during the period (pre-tax amounts of ($309), $10,392, $335 and $7,741)	(185)	6,274	201	4,672
Reclassification adjustment for net gains related to securities available for sale included in net income (pre-tax amounts of $98, $59, $552 and $86)	(58)	(36)	(331)	(52)
Pension and other benefits:
Amortization of prior service cost and actuarial gains (pre-tax amounts of $856, $416, $1,713 and $831)	511	251	1,027	502
Total other comprehensive income	268	6,489	897	5,122
Comprehensive income	$ 13,525	$ 21,144	$ 27,804	$ 34,084