Pension Plans, Other Postretirement Benefits, and Defined-Contribution Plans - Weighted-Average Assumptions for Benefit Obligations Table (Detail)	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.50%	4.50%
Rates of increase in compensation levels	4.50%	4.50%
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.00%	4.75%
Rates of increase in compensation levels	4.50%	4.50%