Fair Value Measurements - Financial Assets and Liabilities Not Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Carrying Amount
Assets:
Cash equivalents	$ 318,260	$ 263,688
Liabilities:
Mortgages payable (excluding deferred debt  issuance costs, net)	1,070,544	974,836
Fair Value | Level 1
Assets:
Cash equivalents	318,260	263,688
Fair Value | Level 2
Liabilities:
Mortgages payable (excluding deferred debt  issuance costs, net)	$ 1,032,000	$ 974,000