Financial Instruments and Fair Value Measurements - Summary of Gains (Losses) From Change in Fair Value of Derivative Instruments Included in Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total derivative hedging instruments	$ 9,829	$ 54,111	$ 46,477
Total derivative and nonderivative hedging instruments – gains (losses)	(467,926)	166,702	367,625
Designated As Hedging Instrument [Member] | Derivative Net Investment Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total derivative hedging instruments	(12,762)	55,460	63,934
Designated As Hedging Instrument [Member] | Interest Rate and Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total derivative hedging instruments	12,726	(551)	(21,714)
Designated As Hedging Instrument [Member] | Our Share of Derivatives from Unconsolidated Co-Investment Ventures [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total derivative hedging instruments	9,865	(798)	4,257
Non-Derivative Net Investment Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Nonderivative net investment hedges	$ (477,755)	$ 112,591	$ 321,148