Investment in Unconsolidated Ventures (Financial Position of Unconsolidated Real Estate Ventures) (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Company's share of equity (Company's basis)		$ 211,771	$ 225,004
Other liabilities		41,630	37,558
Coppell Associates [Member]
Schedule of Equity Method Investments [Line Items]
Other liabilities		1,100	1,200
Unconsolidated Real Estate Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Net property		1,165,941	1,281,282
Other assets		144,415	195,121
Other liabilities		65,290	68,481
Debt		761,067	965,077
Equity		484,000	442,845
Company's share of equity (Company's basis)	[1],[2]	$ 211,771	$ 225,004

[1] Does not include the negative investment balance of one real estate venture totaling $1.1 million as of September 30, 2015 and $1.2 million as of December 31, 2014, 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.