Real Estate Activity During the Nine Months Ended September 30, 2013 Schedule Of Allocation Of The Aggregate Purchase Price Of Acquisition (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended			0 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Apr. 10, 2013 Mountain View Research And Technology Parks [Member]	May 31, 2013 767 Fifth Avenue (The GM Building) [Member]		May 31, 2013 767 Fifth Avenue (The GM Building) [Member]	May 31, 2013 Consolidation, Eliminations [Member] 767 Fifth Avenue (The GM Building) [Member]
Business Acquisition [Line Items]
Land				$ 126,521	$ 1,796,252
Building and improvements				82,451	1,447,446
Tenant improvements				7,326	85,208
In-place lease Intangibles				23,279	357,781
Above market rents				843	101,897
Below market rents				7,336	239,641
Above market assumed debt adjustments					192,943
Net assets acquired				233,084
Real estate and related intangibles recorded upon consolidation	3,356,000	0			3,356,000
Mortgage notes payable	4,468,069		3,102,485		1,300,000
Mezzanine notes payable	311,340		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	181,310		72,461		182,369	[2]		105,500
Other liabilities					6,304
Working capital recorded upon consolidation	97,847	0			(97,847)
Noncontrolling Interet					520,000
Noncontrolling Interet working capital					(39,139)
Noncontrolling interest recorded upon consolidation	(480,861)	0			(480,861)
Net Assets Recorded Upon Consolidation							$ 721,292

[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.