Debt - Summary of Debt (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Property under capital leases [Member]	Dec. 31, 2011 Property under capital leases [Member]
Other Term Debt [Line Items]
Capital lease obligations fixed interest rate	13.00%
Property, plant and equipment, net		$ 309	$ 495
Debt issuance date	Sep. 10, 2012
Senior notes principal amount	600,000
Senior notes interest rate	3.95%
Senior notes maturity	Sep. 15, 2022
Senior notes effective interest rate	3.97%
Senior notes proceeds	593,900
Repurchase agreement maximum loan borrowing capacity	$ 25,000
Expiration date of Repurchase Agreement	Jul. 31, 2013