Financial Instruments and Fair Value Measurements - Additional Information (Detail)	3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2014 USD ($)	Jun. 30, 2013 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2013 USD ($)	Jun. 30, 2014 Foreign Currency Forward Contracts [Member] USD ($)	Dec. 31, 2013 Foreign Currency Forward Contracts [Member] USD ($)	Jun. 30, 2014 Foreign Currency Forward Contracts [Member] EUR (€)	Feb. 28, 2014 Foreign Currency Forward Contracts [Member] USD ($)	Feb. 28, 2014 Foreign Currency Forward Contracts [Member] EUR (€)	Dec. 31, 2013 Foreign Currency Forward Contracts [Member] EUR (€)	Jun. 30, 2014 Foreign Currency Forward Contracts [Member] Operating Partnership [Member] USD ($)	Jun. 30, 2014 Foreign Currency Forward Contracts [Member] Operating Partnership [Member] EUR (€)
Derivative [Line Items]
Outstanding foreign currency put options	$ 0		$ 0
Debt issued	8,524,000,000		8,524,000,000		2,600,000,000	1,000,000,000	1,900,000,000	959,400,000	700,000,000	700,000,000	680,600,000	500,000,000
Amount of gain (loss) included in AOCI	63,464,000	(51,998,000)	58,741,000	(338,252,000)	(4,600,000)	(14,900,000)
Hedge ineffectiveness	$ 0	$ 0	$ 0	$ 0