Noncontrolling Interests (Property Partnerships) (Narrative) (Details) (USD $)	6 Months Ended			0 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Feb. 26, 2013 Salesforece Tower (formerly Transbay Tower) [Member]	Feb. 07, 2013 Salesforece Tower (formerly Transbay Tower) [Member]	May 31, 2013 767 Fifth Avenue (The GM Building) [Member]	May 31, 2013 767 Fifth Avenue (The GM Building) [Member] partners	Oct. 09, 2013 Time Square Tower [Member] sqft	Feb. 26, 2013 Company [Member] Salesforece Tower (formerly Transbay Tower) [Member]
Noncontrolling Interest [Line Items]
Property partnerships	$ 721,096,000		$ 726,132,000
Partners Joint Venture Ownership Percentage				5.00%	50.00%	40.00%
Ownership Percentage									95.00%
Number of Joint Venture Partners							2
Noncontrolling interest recorded upon consolidation	0	483,488,000				480,900,000
maximum percentage of construction costs to allow partner to have a loan				50.00%
Portion of total costs partner can require the company to fund				2.50%
portion of partners equity that can be funded by the company				50.00%
ownership interest sold (percent)								45.00%
Net Contractual Sales Price								684,000,000
Proceeds from sale of an interest in a real estate asset								673,100,000
Net Rentable Area (in sf)								1,246,000
Portion allocation to noncontrolling interest based on carrying value of the total equity of the property prior to the sale								$ 243,500,000