Pension Plans, Other Postretirement Benefits, and Defined-Contribution Plans - Weighted-Average Assumptions for Net Periodic Pension and Other Postretirement Benefit Cost Table (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.50%	4.75%	5.25%
Long-term rate of return on plan assets	7.00%	7.00%	7.50%
Rates of increase in compensation levels	4.50%	5.00%	5.00%
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.75%	5.25%	5.50%
Rates of increase in compensation levels	4.50%	5.00%	5.00%