Pension Benefits - Schedule of Fair Value Measurement (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2012
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Corporate bonds maturity date	Assets invested in two corporate bonds that mature in 2015 and 2020
Asset backed securities maturity date	Assets invested in two asset backed securities. One will mature in 2013 and the other will mature in 2016.
Maturity of high-quality, dollar-denominated, fixed-income securities	397 days or less