Impairment Charges and Reserves - Impairment Charges Measured at Fair Value on Non-Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets held and used, Fair Value Measurements	$ 201,100
Preferred equity interests, Fair Value Measurements	232,000
Preferred equity interests, Total Losses	3,961	$ 76,000
Fair Value Measurements [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets held and used, Fair Value Measurements	201,100
Preferred equity interests, Fair Value Measurements	232,000
Long-lived assets held and used, Total Losses	30,400
Preferred equity interests, Total Losses	4,000
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
Preferred equity interests, 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
Preferred equity interests, 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	201,100
Preferred equity interests, Fair Value Measurements	$ 232,000