Comprehensive Income (Components Of Comprehensive Income, Net Of Related Tax) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net income	$ 29,130	$ 22,362	$ 50,712	$ 39,537
Arising during the period, net of tax expense of $1,279, $1,523, $1,928 and $1,476	2,376	2,830	3,580	2,741
Less: reclassification adjustment for gains included in net income, net of tax expense of $151, $22, $188 and $41	(280)	(41)	(350)	(76)
Pension and postretirement amortization, net of tax expense of $150, $94, $300 and $189	278	174	557	351
Other comprehensive income	2,374	2,963	3,787	3,016
Comprehensive income	$ 31,504	$ 25,325	$ 54,499	$ 42,553