Subsequent Events - Additional Information (Detail) (USD $) In Millions, unless otherwise specified		1 Months Ended						1 Months Ended				1 Months Ended				1 Months Ended						1 Months Ended		1 Months Ended
	Apr. 30, 2013	May 24, 2013 Subsequent Events [Member] Ratio	May 24, 2013 Subsequent Events [Member] Revolving Facility [Member]	May 24, 2013 Subsequent Events [Member] Minimum [Member]	May 24, 2013 Subsequent Events [Member] Maximum [Member]	May 24, 2013 Subsequent Events [Member] U.S. borrowers [Member]	May 24, 2013 Subsequent Events [Member] U.S. borrowers [Member] Revolving Facility [Member]	May 24, 2013 Subsequent Events [Member] U.S. borrowers [Member] Minimum [Member]	May 24, 2013 Subsequent Events [Member] U.S. borrowers [Member] Maximum [Member]	May 24, 2013 Subsequent Events [Member] Canadian borrower [Member]	May 24, 2013 Subsequent Events [Member] Canadian borrower [Member] Revolving Facility [Member]	May 24, 2013 Subsequent Events [Member] Canadian borrower [Member] Minimum [Member]	May 24, 2013 Subsequent Events [Member] Canadian borrower [Member] Maximum [Member]	May 24, 2013 Subsequent Events [Member] Australian borrower [Member]	May 24, 2013 Subsequent Events [Member] Australian borrower [Member] Revolving Facility [Member]	May 24, 2013 Subsequent Events [Member] Australian borrower [Member] Minimum [Member]	May 24, 2013 Subsequent Events [Member] Australian borrower [Member] Maximum [Member]	May 24, 2013 Subsequent Events [Member] Japanese borrower [Member] Revolving Facility [Member]	May 24, 2013 Subsequent Events [Member] U.S. letters of credit [Member] Revolving Facility [Member]	May 24, 2013 Subsequent Events [Member] Canadian letters of credit [Member] Revolving Facility [Member]	May 24, 2013 Subsequent Events [Member] Australian letters of credit [Member] Revolving Facility [Member]	May 24, 2013 Subsequent Events [Member] Japanese letters of credit [Member]	May 24, 2013 Subsequent Events [Member] Japanese letters of credit [Member] Revolving Facility [Member]	May 24, 2013 Subsequent Events [Member] Japanese letters of credit [Member] Minimum [Member]	May 24, 2013 Subsequent Events [Member] Japanese letters of credit [Member] Maximum [Member]
Subsequent Event [Line Items]
Revolving facility maximum borrowing capacity	$ 329						$ 160				$ 30				$ 25			$ 15
Revolving credit facility increase in additional borrowing			125
Sublimit for letters of credit under Revolving Facility																			92.5	12.5	25.0		15.0
Revolving facility term			5 years
Revolving Facility due, in days			91 days
TIBOR rate plus a spread, minimum percentage						1.75%				1.75%				1.75%								1.75%
TIBOR rate plus a spread, maximum percentage						2.25%				2.25%				2.25%								2.25%
Base Rate plus a spread, percentage								0.75%	1.75%			0.75%	1.75%			0.75%	1.75%							0.75%	1.75%
Federal funds effective rate						0.50%				0.50%
Adjusted TIBOR rate interest period						1 month				1 month				1 month								1 month
Adjusted TIBOR rate						1				1				1								1
Bankers' acceptance equivalent rate plus a spread												1.75%	2.25%
Prime Rate												0.75%	1.75%
Bank of Canada overnight rate										0.50%
Bankers' acceptance equivalent rate for interest percentage										1.00%
Bankers' acceptance equivalent rate for interest period										30 days
Australian bank bill rate plus a spread																1.75%	2.25%
Increase in interest rate under Revolving Facility																						2.00%
Fixed charge coverage ratio, minimum		1.0
Fixed charge coverage ratio, maximum		1.0
Aggregate excess availability under the Revolving Facility, amount		$ 15
Aggregate excess availability under the Revolving Facility, as a percentage				10.00%	40.00%