Investment in Unconsolidated Ventures (Financial Position of Unconsolidated Real Estate Ventures) (Details) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Company's share of equity (Company's basis)		$ 201,034	$ 225,004
Coppell Associates [Member]
Schedule of Equity Method Investments [Line Items]
Company's share of equity (Company's basis)		(1,200)	(1,200)
Unconsolidated Real Estate Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Net property		1,295,947	1,281,282
Other assets		165,693	195,121
Other liabilities		59,472	68,481
Debt		927,032	965,077
Equity		475,136	442,845
Company's share of equity (Company's basis)	[1],[2]	$ 201,034	$ 225,004

[1] Does not include the negative investment balance of one real estate venture totaling $1.2 million as of June 30, 2015 and December 31, 2014, respectively, which is included in other liabilities.

[2] This amount includes the effect of the basis difference between the Company's historical cost basis and the basis recorded at the Real Estate Venture level, which is typically amortized over the life of the related assets and liabilities. Basis differentials occur from the impairment of investments, purchases of third party interests in existing Real Estate Ventures and upon the transfer of assets that were previously owned by the Company into a Real Estate Venture. In addition, certain acquisition, transaction and other costs may not be reflected in the net assets at the Real Estate Venture level.