Financial Instruments and Fair Value Measurements - Summary of Gains (Losses) From Change in Fair Value of Derivative Instruments Included in Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total gain (loss) on derivative instruments	$ (1,435)	$ 88,989	$ 36,106	$ 62,609
Total gain (loss) on derivative and nonderivative hedging instruments	(6,109)	293,239	254,835	277,179
Designated As Hedging Instrument [Member] | Derivative Net Investment Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total gain (loss) on derivative instruments	14,225	93,502	48,419	70,393
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total gain (loss) on derivative instruments	(14,680)	(39)	(15,439)	(229)
Designated As Hedging Instrument [Member] | Cash Flow Hedge [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total gain (loss) on derivative instruments	(74)		(74)
Designated As Hedging Instrument [Member] | Our Share of Derivatives from Unconsolidated Co-Investment Ventures [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total gain (loss) on derivative instruments	(906)	(4,474)	3,200	(7,555)
Non-Derivative Net Investment Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Nonderivative net investment hedges	$ (4,674)	$ 204,250	$ 218,729	$ 214,570