Noncontrolling Interests (Property Partnerships) (Narrative) (Details) (USD $)			0 Months Ended			0 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Feb. 26, 2013 Salesforece Tower (formerly Transbay Tower) [Member]	Feb. 07, 2013 Salesforece Tower (formerly Transbay Tower) [Member]	Apr. 10, 2014 Salesforece Tower (formerly Transbay Tower) [Member] sqft	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
Noncontrolling Interest [Line Items]
Property partnerships	$ 725,093,000	$ 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						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					1,400,000			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
Difference between net cash proceeds received and noncontrolling interest recognized								$ 429,600,000