Real Estate Activity During the Six Months Ended June 30, 2013 Schedule Of Allocation Of The Aggregate Purchase Price Of Acquisition (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended			0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	May 31, 2013 767 Fifth Avenue (The GM Building) [Member]		Apr. 10, 2013 Mountain View Research And Technology Parks [Member]	May 31, 2013 Consolidation, Eliminations [Member] 767 Fifth Avenue (The GM Building) [Member]
Business Acquisition [Line Items]
Land				$ 1,796,252		$ 126,521
Building and Improvements				1,447,446		82,451
Tenant Improvements				85,208		7,326
In place Intangibles				357,781		23,279
Above market rents				101,897		843
Below market rents				(239,641)		(7,336)
Above market assumed debt adjustments				(192,943)
Net assets required						233,084
Real estate and realted intangibles recorded upon consolidation	3,356,000	0		3,356,000
Mortgage notes payable	4,484,657		3,102,485	1,300,000
Mezzanine notes payable	311,637		0	306,000
Related party notes payable	(180,000)		0	(450,000)	[1]		(270,000)
Debt recorded upon consolidation	2,056,000	0		2,056,000
Cash and cash equivalents	79,468	0		79,468
Cash held in escrows				2,403
Tenant and other receivables				7,104
Prepaid expense and other assets				4,269
Accounts payable and accrued expenses				(2,418)
Accrued interest payable	(141,676)		(72,461)	(175,802)	[2]		(105,500)
Other Liabilities				(6,304)
Working capital recorded upon consolidation	91,280	0		(91,280)
Noncontrolling Interet				(520,000)
Noncontrolling interet working capital				36,512
Noncontrolling interest recorded upon consolidation	(483,488)	0		(483,488)
Net assets recorded upon consolidation				$ 725,232

[1] (1) The Company's partner loans totaling $270.0 million eliminates in consolidation.

[2] The Company's share of the accrued interest payable on the partner loans totaling approximately $105.5 million eliminates in consolidation.