Discontinued Operations Discontinued Operations (Details) (USD $)	3 Months Ended
	Mar. 31, 2012 RSF NumberofBuildings		Mar. 31, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings	7
Rentable square feet	374,139
Net proceeds from disposition held by a qualified intermediary in connection wtih Section 1031 exchange	$ 42,395,000		$ 0
Rental income	90,219,000		76,997,000
Tenant reimbursements	8,304,000		6,022,000
Other property income	887,000		754,000
Property expenses	17,535,000		17,509,000
Real estate taxes	8,389,000		7,890,000
Depreciation and amortization	36,746,000		28,441,000
Income from discontinued operations before net gain on dispositions of discontinued operations	900,000		3,023,000
Net gain on dispositions of discontinued operations	72,809,000		0
Total income from discontinued operations	73,709,000	[1]	3,023,000	[1],[2]
Total Property Dispositions [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable square feet			282,611
Rental income	870,000		3,293,000
Tenant reimbursements	133,000		400,000
Other property income	0		659,000
Total revenues	1,003,000		4,352,000
Property expenses	27,000		180,000
Real estate taxes	70,000		279,000
Depreciation and amortization	6,000		870,000
Total expenses	103,000		1,329,000
Income from discontinued operations before net gain on dispositions of discontinued operations	900,000		3,023,000
Net gain on dispositions of discontinued operations	72,809,000		0
Total income from discontinued operations	73,709,000		3,023,000
15004 Innovation Drive and 10243 Genetic Center Drive, San Diego, CA [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Property Type	Office	[3]
Month of Disposition	January	[3]
Number of Buildings	2	[3]
Rentable square feet	253,676	[3]
Sales Price	146,100,000	[3]
Net proceeds from disposition held by a qualified intermediary in connection wtih Section 1031 exchange	42,395,000
Reportable Segment - Office Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings	7
Rentable square feet	374,139
Total income from discontinued operations	73,709,000		2,309,000
Reportable Segment - Office Properties [Member] | Total Property Dispositions [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings			2
All Other Segments [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total income from discontinued operations	$ 0		$ 714,000
All Other Segments [Member] | Total Property Dispositions [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Buildings			1

[1] See Note 14 for the breakdown of income from discontinued operations by segment.

[2] Includes two office and one industrial buildings encompassing 282,611 rentable square feet that were disposed of in 2011.

[3] Properties were classified as held for sale on the consolidated balance sheets as of December 31, 2011.