Discontinued Operations (Details) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended					0 Months Ended
	Sep. 30, 2013 building sqft	Sep. 30, 2012	Sep. 30, 2013 building sqft	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Agoura Road, 26541, Calabasas, CA [Member] sqft building	Sep. 30, 2013 San Diego Properties, San Diego, CA [Member] sqft		Sep. 30, 2013 Kaiser Boulevard, Anaheim, California [Member] sqft		Oct. 02, 2013 Subsequent Event [Member] Kaiser Boulevard, Anaheim, California [Member]	Sep. 30, 2013 Other Segments [Member] Properties Held for Sale [Member] building		Sep. 30, 2013 Other Segments [Member] San Diego, California [Member] Properties Held for Sale [Member] building		Sep. 30, 2013 Other Segments [Member] Anaheim, California [Member] Properties Held for Sale [Member] building
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings	14		14			1						14	[1]	13	[2],[3]	1	[2],[4]
Rentable Square Feet	1,159,185		1,159,185			90,156	1,099,395	[3]	59,790	[4]
Dispositions Sales Price						$ 14,700,000					$ 9,600,000
Disposal Group, Including Discontinued Operation, Balance Sheet Disclosures [Abstract]
Land and improvements	54,273,000		54,273,000
Buildings and improvements	236,792,000		236,792,000
Undeveloped land and construction in progress	1,441,000		1,441,000
Total real estate held for sale	292,506,000		292,506,000
Accumulated depreciation	(70,084,000)		(70,084,000)
Total real estate held for sale, net	222,422,000		222,422,000
Current receivables, net	303,000		303,000
Deferred rent receivables, net	9,062,000		9,062,000
Deferred leasing costs and acquisition-related intangible assets, net	6,643,000		6,643,000
Prepaid expenses and other assets, net	981,000		981,000
Real estate and other assets held for sale, net	239,411,000		239,411,000		0
Accounts payable and other liabilities	2,554,000		2,554,000
Deferred revenue and acquisition-related intangible liabilities, net	12,785,000		12,785,000
Rents received in advance and tenant security deposits	1,412,000		1,412,000
Liabilities and deferred revenue of real estate assets held for sale	16,751,000		16,751,000		0
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Rental income	6,604,000	10,522,000	18,334,000	33,105,000
Tenant reimbursements	892,000	1,639,000	2,331,000	5,296,000
Other property income	4,610,000	229,000	4,617,000	884,000
Total revenues	12,106,000	12,390,000	25,282,000	39,285,000
Property expenses	2,020,000	2,044,000	3,920,000	6,287,000
Real estate taxes	684,000	1,301,000	2,048,000	3,719,000
Provision for bad debts	(23,000)	(194,000)	(23,000)	(194,000)
Depreciation and amortization	3,081,000	4,550,000	8,531,000	13,870,000
Total expenses	5,762,000	7,701,000	14,476,000	23,682,000
Income from discontinued operations before net gain on dispositions of discontinued operations	6,344,000	4,689,000	10,806,000	15,603,000
Net gain on dispositions of discontinued operations	0	0	423,000	72,809,000
Total income from discontinued operations	$ 6,344,000	$ 4,689,000	$ 11,229,000	$ 88,412,000

[1] Includes 13 properties located in San Diego, California and one property in Anaheim, California (see Note 12).

[2] Estimated rentable square feet upon completion.

[3] The San Diego Properties included the following: 4910 Directors Place, 10020 Pacific Mesa Boulevard, 6055 Lusk Avenue, 5010 and 5005 Wateridge Vista Drive, 15435 and 15445 Innovation Drive, and 15051, 15073, 15231, 15253, 15333 and 15378 Avenue of Science.

[4] We closed on the disposition of this property on October 2, 2013. The sales price was $9.6 million.