Pension and Other Postretirement Benefits - Schedule of Weighted Average Assumptions Used to Determine Net Periodic Cost (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.90%	5.75%	6.15%
Expected long-term rate of return on plan assets	8.50%	8.50%	8.75%	8.75%	9.00%
Rate of compensation increase	3.50%	3.50%	3.50%