Impairment Charges and Reserves - Impairment Charges on Assets or Investments (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Impairment Charges And Impairment Of Joint Venture Investments [Abstract]
Assets marketed for sale	$ 18,100	$ 19,000	$ 48,500	$ 41,000
(Adjustment) reserve of preferred equity interests	(1,625)	0	2,336	76,000
Total impairment charges	16,500	28,100	50,800	126,100
Undeveloped Land [Member]
Impairment Charges And Impairment Of Joint Venture Investments [Abstract]
Undeveloped land	$ 0	$ 9,100	$ 0	$ 9,100

The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Period Type:	duration