Fair Value Measurements - Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of mortgage and other indebtedness	$ 941,801	$ 1,091,745
Estimated fair value of secured line of credit and secured term loan liabilities subject to compromise.	2,042,994	1,606,959
Available-For-Sale Securities Held, Amortized Cost	99,991	233,053
Available-For-Sale Securities Held, Fair Value	99,998	233,071
U.S Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-For-Sale Securities Held, Amortized Cost	99,991	233,053
Available-For-Sale Securities Held, Unrealized gain	7	18
Available-For-Sale Securities Held, Fair Value	$ 99,998	$ 233,071
U.S. Treasury securities, maturity date	Oct. 31, 2021