Investments in and Advances to Joint Ventures - Service Fees and Income Earned by Company's Unconsolidated Joint Ventures and Interest Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue from contracts with customers:
Total revenue from contracts with customers	$ 14,394	$ 6,499	$ 28,437	$ 23,051
Other:
Interest income	4,800	6,300	14,600	20,000
Other	700	700	1,900	2,100
Total fee and other income	11,000	13,500	36,100	45,200
Asset and Property Management Fees [Member]
Revenue from contracts with customers:
Total revenue from contracts with customers	10,501	4,660	20,982	16,851
Unconsolidated Joint Ventures [Member]
Revenue from contracts with customers:
Total revenue from contracts with customers	5,500	6,500	19,600	23,100
Unconsolidated Joint Ventures [Member] | Asset and Property Management Fees [Member]
Revenue from contracts with customers:
Total revenue from contracts with customers	4,000	4,700	14,500	16,900
Unconsolidated Joint Ventures [Member] | Development Fees and Leasing Commissions [Member]
Revenue from contracts with customers:
Total revenue from contracts with customers	$ 1,500	$ 1,800	$ 5,100	$ 6,200