Fair Value Measurements - Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Restricted cash	$ 5,882	$ 4,982	$ 3,982
Notes payable, excluding deferred loan costs	761,794	908,893
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	10,669	17,885,000
Restricted cash	5,882	4,982,000
Notes payable, excluding deferred loan costs	766,564	915,779,000
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	10,669	17,885,000
Restricted cash	5,882	4,982,000
Notes payable, excluding deferred loan costs	$ 694,237,000	$ 846,134,000