Investment in Unconsolidated Joint Ventures - Balance Sheet of Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Real estate, net	$ 2,968,222	$ 3,024,271
Receivables and other assets	331,588	285,217
Total assets	3,592,702	3,704,714
Mortgage debt	1,193,953	1,339,450
Total liabilities and equity	3,592,702	3,704,714
Equity Method Investee
Schedule of Equity Method Investments [Line Items]
Cash	310	1,364
Restricted cash	397	269
Real estate, net	95,513	96,164
Intangible assets, net	3,624	5,232
Receivables and other assets	8,370	6,926
Total assets	108,214	109,955
Mortgage debt	46,189	43,441
Other liabilities	1,936	1,931
Partners' equity	60,089	64,583
Total liabilities and equity	108,214	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	46,473	47,632
Intangible assets, net	2,333	2,537
Receivables and other assets	3,454	3,365
Total assets	52,404	53,680
Mortgage debt	13,189	13,441
Other liabilities	382	370
Partners' equity	38,833	39,869
Total liabilities and equity	52,404	53,680
Equity Method Investee | 7000 Central Park
Schedule of Equity Method Investments [Line Items]
Cash	166	1,218
Restricted cash	397	269
Real estate, net	49,040	48,532
Intangible assets, net	1,291	2,695
Receivables and other assets	4,916	3,561
Total assets	55,810	56,275
Mortgage debt	33,000	30,000
Other liabilities	1,554	1,561
Partners' equity	21,256	24,714
Total liabilities and equity	$ 55,810	$ 56,275