Schedule Of Expected Cash Flow For Pension And Post Retirement Benefit Plans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Pension Plan Asset
Schedule Of Defined Contribution Pension And Other Postretirement Plans Disclosure [Line Items]
Expected employer contributions, 2013	$ 22,450
Pension Plan Asset | To Plan Trusts
Schedule Of Defined Contribution Pension And Other Postretirement Plans Disclosure [Line Items]
Expected employer contributions, 2013	67,075
Pension Plan Asset | To Plan Participants
Schedule Of Defined Contribution Pension And Other Postretirement Plans Disclosure [Line Items]
Expected employer contributions, 2013	1,900
Postretirement Benefit Plan Assets
Schedule Of Defined Contribution Pension And Other Postretirement Plans Disclosure [Line Items]
Expected employer contributions, 2013	7,624
Postretirement Benefit Plan Assets | To Plan Trusts
Schedule Of Defined Contribution Pension And Other Postretirement Plans Disclosure [Line Items]
Expected employer contributions, 2013	27,985
Postretirement Benefit Plan Assets | To Plan Participants
Schedule Of Defined Contribution Pension And Other Postretirement Plans Disclosure [Line Items]
Expected employer contributions, 2013	$ 78