Derivative Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified		9 Months Ended
	Sep. 30, 2012 Derivative	Sep. 30, 2012 Interest Rate Swaps [Member]	Sep. 30, 2012 Senior Notes, interest at [6.25]%, maturing [2013] [Member]	Dec. 31, 2011 Senior Notes, interest at [6.25]%, maturing [2013] [Member]	Sep. 30, 2012 Three Interest Rate Swap Agreements [Member]	Sep. 30, 2012 Euro Forward Contracts [Member] Derivative	Sep. 30, 2012 Three Interest Rate Swap 2013 Agreements [Member] PartnershipUnit
Derivative Financial Instruments [Line Items]
Notional dollar amount of forward contracts						$ 28
Average exchange rate on forward contracts						1.3
Maturity period of forward contract	Less than one year
Number of interest rate swap agreements	3
Notional amount of interest rate swaps			250		150		250
Terminated number of interest rate swap agreements							3
Gain recorded to interest expense		$ 3
Interest rate, stated rate			6.25%	6.25%