Comprehensive Income (Components Of Comprehensive Income, Net Of Related Tax) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Comprehensive Income [Abstract]
Net income	$ 21,582	$ 17,175
Arising during the period, net of tax expense (benefit) of $649 and $(48)	1,205	(89)
Less: reclassification adjustment for gains included in net income, net of tax expense of $38 and $19	(70)	(35)
Pension and postretirement amortization, net of tax expense of $150 and $96	278	177
Other comprehensive income	1,413	53
Comprehensive income	22,995	17,228
Unrealized (losses) gains on securities: Arising during the period, net of tax expense (benefit)	649	(48)
Unrealized (losses) gains on securities: Less: reclassification adjustment for gains included in net income, net of tax expense	38	19
Other comprehensive income: Pension and postretirement amortization, net of tax expense	$ 150	$ 96