Investment in Unconsolidated Joint Ventures - Balance Sheet of Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Real estate, net	$ 3,000,361	$ 3,024,271
Receivables and other assets	279,151	285,217
Total assets	3,626,735	3,704,714
Mortgage debt	1,201,806	1,339,450
Total liabilities and equity	3,626,735	3,704,714
Equity Method Investee
Schedule of Equity Method Investments [Line Items]
Cash	1,595	1,364
Restricted cash	274	269
Real estate, net	95,876	96,164
Intangible assets, net	4,044	5,232
Receivables and other assets	7,763	6,926
Total assets	109,552	109,955
Mortgage debt	46,273	43,441
Other liabilities	2,250	1,931
Partners' equity	61,029	64,583
Total liabilities and equity	109,552	109,955
Equity Method Investee | US Airways Building
Schedule of Equity Method Investments [Line Items]
Cash	144	146
Restricted cash	0	0
Real estate, net	46,859	47,632
Intangible assets, net	2,401	2,537
Receivables and other assets	3,437	3,365
Total assets	52,841	53,680
Mortgage debt	13,273	13,441
Other liabilities	379	370
Partners' equity	39,189	39,869
Total liabilities and equity	52,841	53,680
Equity Method Investee | 7000 Central Park JV LLC
Schedule of Equity Method Investments [Line Items]
Cash	1,451	1,218
Restricted cash	274	269
Real estate, net	49,017	48,532
Intangible assets, net	1,643	2,695
Receivables and other assets	4,326	3,561
Total assets	56,711	56,275
Mortgage debt	33,000	30,000
Other liabilities	1,871	1,561
Partners' equity	21,840	24,714
Total liabilities and equity	$ 56,711	$ 56,275