Reclassifications Out of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax effect	$ (111)	$ (103)	$ (326)	$ (304)
Tax effect	(1,566)	(1,026)	(2,605)	(2,859)
Amounts reclassified from accumulated other comprehensive loss, net of tax	2,555	1,608	6,782	5,178
Accumulated Defined Benefit Plans Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss, net of tax	2,387	1,451	6,285	4,714
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Settlement charge	729	255	729	779
Prior service credit	(702)	(704)	(2,104)	(2,092)
Actuarial loss	3,926	2,849	11,779	9,111
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Tax, Total	3,953	2,400	10,404	7,798
Tax effect	(1,566)	(949)	(4,119)	(3,084)
Amounts reclassified from accumulated other comprehensive loss, net of tax	2,387	1,451	6,285	4,714
Accumulated Net Gain Loss From Terminated Forward Starting Interest Rate Swap
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from accumulated other comprehensive loss, net of tax	168	157	497	464
Accumulated Net Gain Loss From Terminated Forward Starting Interest Rate Swap | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Additional interest expense	279	260	823	768
Tax effect	(111)	(103)	(326)	(304)
Amounts reclassified from accumulated other comprehensive loss, net of tax	$ 168	$ 157	$ 497	$ 464