Real Estate - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Real Estate Properties [Line Items]
Gains on acquisitions and dispositions of investments in real estate, net	$ 338,845	$ 267,771
Europe [Member]
Real Estate Properties [Line Items]
Gains on acquisitions and dispositions of investments in real estate, net	1,800
Japan [Member]
Real Estate Properties [Line Items]
Gains on acquisitions and dispositions of investments in real estate, net	$ 337,900