Foreign Currency Sale Contracts (Detail) (Foreign Exchange Contract)	3 Months Ended		3 Months Ended
	Mar. 31, 2015 Foreign Currency Forward Sale Contract 1 European Joint Venture USD ($)	Mar. 31, 2015 Foreign Currency Forward Sale Contract 1 European Joint Venture EUR (€)	Mar. 31, 2015 Foreign Currency Forward Sale Contract 2 Canadian Properties USD ($)	Mar. 31, 2015 Foreign Currency Forward Sale Contract 2 Canadian Properties CAD
Derivative [Line Items]
Transaction Date Range	July 2011-May 2014		November 2014
Total transaction amount	$ 135,000,000	€ 100,000,000	$ 22,000,000	25,000,000
Forward purchase date range	August 2015-May 2017		November 2016
Change in fair value gain (loss)	$ 14,000,000		$ 1,000,000