Impairment Charges and Impairment of Joint Venture Investments - Impairment Charges Measured at Fair Value on Non-Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of joint venture investments	$ 0	$ 0	$ 0	$ 9,100
Fair Value Measurements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unconsolidated joint venture investments, Fair Value Measurements					$ 6,400
Long-lived assets held and used, Fair Value Measurements	407,100		407,100		141,200
Long-lived assets held and used, Total Losses			279,000		38,100
Impairment of joint venture investments					30,700
Fair Value Measurements [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets held and used, Fair Value Measurements	0		0		0
Unconsolidated joint venture investments, Fair Value Measurements					0
Fair Value Measurements [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets held and used, Fair Value Measurements	0		0		0
Unconsolidated joint venture investments, Fair Value Measurements					0
Fair Value Measurements [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets held and used, Fair Value Measurements	$ 407,100		$ 407,100		141,200
Unconsolidated joint venture investments, Fair Value Measurements					$ 6,400