Discontinued Operations (Details 1) (USD $)	3 Months Ended																12 Months Ended															12 Months Ended
	Dec. 31, 2012 sqft		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012 sqft		Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Total Property Dispositions [Member] sqft building		Dec. 31, 2011 Total Property Dispositions [Member] building sqft		Dec. 31, 2010 Total Property Dispositions [Member] sqft building		Dec. 31, 2012 Innovation Drive and Genetic Center Drive, San Diego, CA [Member] building sqft	Dec. 31, 2012 Industrial Portfolio and Other Properties [Member] sqft building	Dec. 31, 2012 Industrial Portfolio [Member] sqft building	Dec. 31, 2012 Carmino Ruiz CA [Member] sqft building	Dec. 31, 2012 4175 E. La Palma Avenue, Anaheim, California [Member] building sqft	Dec. 31, 2011 10350 Barnes Canyon and 10120 Pacific Heights Drive San Diego CA Disposition [Member] building sqft	Dec. 31, 2011 2031 E Mariposa Avenue, Los Angeles, CA [Member] building sqft	Dec. 31, 2010 660 N Puente Street Brea CA Disposition [Member] sqft building	Dec. 31, 2010 601 Valencia Avenue Brea CA Disposition [Member] building sqft	Dec. 31, 2010 603 Valencia Avenue Brea CA Disposition [Member] building sqft	Dec. 31, 2012 Office Properties [Member] sqft		Dec. 31, 2011 Office Properties [Member]	Dec. 31, 2010 Office Properties [Member]	Dec. 31, 2012 Industrial Properties [Member]		Dec. 31, 2011 Industrial Properties [Member]		Dec. 31, 2010 Industrial Properties [Member]		Oct. 31, 2011 Mortgage Loans on Real Estate [Member] Total Property Dispositions [Member] property	Dec. 31, 2012 Restricted cash [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash Received from Divestiture of Businesses																																																$ 228,800,000
Property Type																											Office		Industrial			Office	Industrial	Industrial	Office	Office
Month of Disposition																											January		November/December			September	December	October	December	December
Number of buildings																					46		3		3		2	44	39	4	1	2	1	1	1	1
Rentable square feet	13,249,780	[1]															13,249,780	[1]			3,975,665		282,611		158,358		253,676	3,721,989	3,413,354	265,372	43,263	90,558	192,053	51,567	60,891	45,900	13,249,780	[1]
Sales Price																					500,300,000		66,100,000		15,800,000		146,100,000	354,200,000				23,900,000	42,200,000	5,000,000	5,400,000	5,400,000
Rental income																	369,516,000		307,118,000	235,304,000	22,337,000		39,226,000		39,404,000
Tenant reimbursements																	32,309,000		23,977,000	17,996,000	3,902,000		5,502,000		6,330,000
Other property income																	3,087,000		6,534,000	1,694,000	323,000		790,000		1,252,000
Total revenues																					26,562,000		45,518,000		46,986,000
Property expenses																	79,357,000		66,821,000	51,169,000	4,586,000		6,733,000		6,898,000
Real estate taxes																	34,479,000		29,633,000	23,474,000	2,779,000		4,000,000		4,020,000
Provision for bad debts																	(153,000)		(781,000)	(65,000)	195,000		137,000		1,128,000
Depreciation and amortization																	162,917,000		124,928,000	90,836,000	6,983,000		11,668,000		12,973,000
Interest expense																					0	[2]	3,624,000	[2]	4,859,000	[2]
Total expenses																					14,153,000		25,888,000		27,622,000
Income from discontinued operations before net gain on dispositions of discontinued operations																	12,409,000		19,630,000	19,364,000	12,409,000		19,630,000		19,364,000
Net gain on dispositions of discontinued operations																	259,245,000		51,587,000	949,000	259,245,000		51,587,000		949,000
Total income from discontinued operations	189,720,000	[3]	3,187,000	[3]	2,241,000	[3]	76,506,000	[3]	44,876,000	[3]	17,681,000	[3]	4,543,000	[3]	4,117,000	[3]	271,654,000		71,217,000	20,313,000	271,654,000		71,217,000		20,313,000												77,157,000		20,535,000	7,673,000	194,497,000	[4]	50,682,000	[4]	12,640,000	[4]
Principal amount																																															$ 70,000,000
Number of properties, collateral																																															13

[1] Includes square footage from our stabilized portfolio.

[2] Interest expense relates to a $70.0 million mortgage loan that was secured by 13 of our industrial properties. The mortgage loan was repaid in October 2011 prior to maturity.

[3] All periods have been adjusted from amounts previously disclosed in our quarterly filings on Form 10-Q to reclassify amounts related to discontinued operations (see Note 17).

[4] The industrial properties were no longer a segment at December 31, 2012 because we disposed of all of our industrial properties during the fourth quarter of 2012.