Pro Forma Results of the Company (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				7 Months Ended		9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2012		Sep. 30, 2011
Pro forma Results of the Company
Revenues	$ 104,910	[1]	$ 93,882	[1]			$ 303,014	[1]	$ 261,853	[1]
Net (loss) income available to common stockholders	(2,793)	[1],[2],[3]	9,841	[1],[2],[3]			62,202	[1],[2],[3]	4,918	[1],[2],[3]
Net (loss) income available to common stockholders per share - basic	$ (0.04)	[1],[2],[3]	$ 0.17	[1],[2],[3]			$ 0.90	[1],[2],[3]	$ 0.07	[1],[2],[3]
Net (loss) income available to common stockholders per share - diluted	$ (0.04)	[1],[2],[3]	$ 0.17	[1],[2],[3]			$ 0.90	[1],[2],[3]	$ 0.07	[1],[2],[3]
Actual results for material acquisitions
Revenues					11,248
Net income					2,342	[4]
Pro Forma Results of the Company (Textuals) [Abstract]
Acquisition-related expenses	556		1,163				3,897		2,829
Material Acquisitions [Member]
Pro Forma Results of the Company (Textuals) [Abstract]
Purchase price for material acquistions as a percentage of the total purchase price of all acquisitions	61.00%				61.00%		61.00%
4100-4700 Bohannon Drive, Menlo Park, CA [Member]
Pro Forma Results of the Company (Textuals) [Abstract]
Acquisition-related expenses	$ 200						$ 900

[1] The purchase of 4100-4700 Bohannon Drive, Menlo Park, CA and 10900 Northeast 4th Street, Bellevue, WA, represent the largest acquisitions and 61% of the total aggregate purchase price of the operating properties acquired during the nine months ended September 30, 2012.

[2] The pro forma results for all periods presented includes incremental interest expense assuming the acquisitions were funded by pro forma borrowings under the Credit Facility. The pro forma interest expense estimate is calculated based on the actual interest rate in effect on the Credit Facility for each respective period. Actual funding of the acquisitions may be from different sources and the pro forma borrowings and related pro forma interest expense estimate assumed herein are not indicative of actual results.

[3] The pro forma results for the three and nine months ended September 30, 2012 were adjusted to exclude acquisition-related expenses of approximately $0.2 million and $0.9 million, respectively, incurred in 2012 for the acquisition of 4100-4700 Bohannon Drive, Menlo Park, CA and 10900 Northeast 4th Street, Bellevue, WA. The pro forma results for the three and nine months ended September 30, 2011 were adjusted to include these expenses.

[4] Reflects the net operating income less depreciation for these properties and amortization of lease-related intangibles.