Schedule Of Amounts Recognized In Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Net amounts recognized at year end	$ 168,129	$ 119,863	$ 105,903	$ 93,674
Pension Benefits
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Net loss (gain)	156,567	111,964
Prior service cost	7,752	6,446
Transition obligation	0	0
Net amounts recognized at year end	$ 164,319	$ 118,410