Debt - Debt Summary (Parenthetical) (Detail) (USD $)	12 Months Ended							12 Months Ended			12 Months Ended
	Dec. 31, 2013 Property	Dec. 31, 2013 Minimum [Member]	Dec. 31, 2013 Maximum [Member]	Dec. 31, 2013 Senior notes [Member] Minimum [Member]	Dec. 31, 2013 Senior notes [Member] Maximum [Member]	Dec. 31, 2013 Exchangeable senior notes [Member]	Dec. 31, 2012 Exchangeable senior notes [Member]	Dec. 31, 2013 Secured mortgage debt [Member] Minimum [Member]	Dec. 31, 2013 Secured mortgage debt [Member] Maximum [Member]	Dec. 31, 2013 Other debt [Member]	Dec. 31, 2013 Secured Mortgage Debt [Member] Minimum [Member]	Dec. 31, 2013 Secured Mortgage Debt [Member] Maximum [Member]	Dec. 31, 2013 Euro [Member]	Dec. 31, 2013 Japanese Yen [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Foreign principal borrowing included in total debt denominated in non-U.S. dollars													$ 1,500,000,000	$ 400,000,000
Interest Rate				2.80%	9.30%			0.50%	7.60%		1.90%	7.20%
Debt Instrument maturity date		2014-02	2033-09	2015-02	2023-08			2014-05	2025-04		2014-12	2027-12
Weighted average coupon interest rate						3.30%	2.80%
Count of properties securing mortgage debt	296
Cost of properties securing mortgage debt	4,200,000,000
Count of properties securing consolidated investees mortgage debt	36
Cost of properties securing consolidated investees mortgage debt	500,000,000
Interest rates of bonds issued, minimum	4.50%
Interest rates of bonds issued, maximum	7.90%
Aggregate unpredictable cost of properties										$ 838,400,000