Weighted-Average Assumptions Used to Determine Net Periodic Benefit Expense (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Net Periodic Benefit Costs Weighted Average Assumptions [Line Items]
Expected return on plan assets	7.85%
Pension Plans
Schedule of Net Periodic Benefit Costs Weighted Average Assumptions [Line Items]
Discount rate	4.25%	5.39%	5.95%
Expected return on plan assets	7.85%	8.35%	8.35%
Rate of compensation increase	4.00%	4.00%	4.00%
Other Retirement Plans
Schedule of Net Periodic Benefit Costs Weighted Average Assumptions [Line Items]
Discount rate	4.05%	5.15%	5.75%