Investment in Unconsolidated Joint Ventures Balance Sheet of Unconsolidated Joint Ventures (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Real estate, net	$ 2,329,405	$ 2,316,795
Total assets	3,003,409	2,925,501
Mortgage debt	1,093,428	1,097,493
Total liabilities & partners' equity	3,003,409	2,925,501
Equity Method Investee
Schedule of Equity Method Investments [Line Items]
Cash	10,318
Restricted cash	1,215
Real estate, net	817,016
Intangible assets, net	68,600
Other assets	15,960
Total assets	913,109
Mortgage debt	671,598
Other liabilities	41,117
Partners' equity	200,394
Total liabilities & partners' equity	913,109
Equity Method Investee | US Airways Building
Schedule of Equity Method Investments [Line Items]
Cash	2,284
Restricted cash	0
Real estate, net	48,790
Intangible assets, net	5,486
Other assets	474
Total assets	57,034
Mortgage debt	13,693
Other liabilities	363
Partners' equity	42,978
Total liabilities & partners' equity	57,034
Equity Method Investee | 7000 Central Park JV LLC
Schedule of Equity Method Investments [Line Items]
Cash	2,433
Restricted cash	153
Real estate, net	48,979
Intangible assets, net	6,572
Other assets	935
Total assets	59,072
Mortgage debt	30,000
Other liabilities	2,021
Partners' equity	27,051
Total liabilities & partners' equity	59,072
Equity Method Investee | Austin Joint Venture
Schedule of Equity Method Investments [Line Items]
Cash	5,601
Restricted cash	1,062
Real estate, net	719,247
Intangible assets, net	56,542
Other assets	14,551
Total assets	797,003
Mortgage debt	627,905
Other liabilities	38,733
Partners' equity	130,365
Total liabilities & partners' equity	$ 797,003