Financial Instruments and Fair Value Measurements - Non-Financial Assets Measured at Fair Value on Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Mar. 31, 2012	Sep. 30, 2012	Sep. 30, 2011
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Discontinued Operations - operating properties - Fair value	$ 259,825		$ 259,825	$ 72,425
Total real estate assets - Fair value	280,087		280,087	72,425
Investments in unconsolidated entities - Fair Value				31,518
Total other assets - Fair value	17,667		17,667	31,518
Discontinued Operations - operating properties - Impairments	27,409		27,409	2,659
Total real estate assets - Impairments	40,372		40,372	2,659
Investments in unconsolidated entities - Impairments				103,823
Total other assets - Impairments		16,135	16,135	103,823
Other Assets [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total other assets - Fair value	17,667		17,667
Total other assets - Impairments			16,135
Operating Properties [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total real estate assets - Fair value	9,442		9,442
Total real estate assets - Impairments	3,187		3,187
Land [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Total real estate assets - Fair value	10,820		10,820
Total real estate assets - Impairments	$ 9,776		$ 9,776