Fair Value Measurements - Financial Assets and Liabilities Not Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Carrying Amount
Assets:
Cash equivalents	$ 412,592	$ 393,070
Liabilities:
Mortgages payable (excluding deferred debt  issuance costs, net)	1,164,544	1,164,544
Fair Value | Level 1
Assets:
Cash equivalents	412,592	393,070
Fair Value | Level 2
Liabilities:
Mortgages payable (excluding deferred debt  issuance costs, net)	$ 1,130,000	$ 1,130,000