Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	$ 42,414	$ 43,191
Total assets	42,414	43,191
Liabilities measured at fair value	0	0
Interest rate cap (included in other assets)	0	0
Carrying Reported Amount Fair Value Disclosure [Member]
Assets
Cash Equivalents	222,929	226,476
Liabilities
Mortgages payable (excluding deferred debt issuance costs, net)	1,058,751	1,059,587
Fair Value, Inputs, Level 1 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	42,414	43,191
Total assets	42,414	43,191
Fair Value, Inputs, Level 1 [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]
Assets
Cash Equivalents	222,929	226,476
Fair Value, Inputs, Level 2 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	0	0
Total assets	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate Of Fair Value Fair Value Disclosure [Member]
Liabilities
Mortgages payable (excluding deferred debt issuance costs, net)	1,044,000	1,054,000
Fair Value, Inputs, Level 3 [Member]
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	0	0
Total assets	$ 0	$ 0