Impairment Charges and Impairment of Joint Venture Investments - Impairment Charges Measured at Fair Value on Non-Recurring Basis (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Unconsolidated joint venture investments, Total Losses	$ 26,671,000	$ 2,921,000	$ 227,000
Fair Value Measurements [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Long-lived assets held and used and held for sale, Fair Value Measurements	180,700,000	212,000,000	229,200,000
Unconsolidated joint venture investments, Fair Value Measurements	4,700,000	5,500,000	0
Deconsolidated joint venture investment, Fair Value Measurements	56,100,000
Long-lived assets held and used and held for sale, Total Losses	126,500,000	125,800,000	171,900,000
Unconsolidated joint venture investments, Total Losses	26,700,000	2,900,000	200,000
Deconsolidated joint venture investment, Total Losses	9,300,000
Fair Value Measurements [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Long-lived assets held and used and held for sale, Fair Value Measurements	0	0	0
Unconsolidated joint venture investments, Fair Value Measurements	0	0	0
Deconsolidated joint venture investment, Fair Value Measurements	0
Fair Value Measurements [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Long-lived assets held and used and held for sale, Fair Value Measurements	0	0	0
Unconsolidated joint venture investments, Fair Value Measurements	0	0	0
Deconsolidated joint venture investment, Fair Value Measurements	0
Fair Value Measurements [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Long-lived assets held and used and held for sale, Fair Value Measurements	180,700,000	212,000,000	229,200,000
Unconsolidated joint venture investments, Fair Value Measurements	4,700,000	5,500,000	0
Deconsolidated joint venture investment, Fair Value Measurements	$ 56,100,000