Pro Forma Results of the Company (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	1 Months Ended		3 Months Ended
	Mar. 31, 2012		Mar. 31, 2012		Mar. 31, 2011
Pro forma Results of the Company
Revenues			$ 101,549		$ 86,729
Net income available to common stockholders			68,265	[1],[2]	80	[1],[2]
Net income available to common stockholders per share - basic			$ 1.07	[1],[2]	$ 0.00	[1],[2]
Net income available to common stockholders per share - diluted			$ 1.07	[1],[2]	$ 0.00	[1],[2]
Actual results for material acquisitions
Revenues	1,179
Net income	213	[3]
Pro Forma Results of the Company (Textuals) [Abstract]
Acquisition-related expenses			1,528		472
Bohannon Drive Menlo Park, CA [Member]
Pro Forma Results of the Company (Textuals) [Abstract]
Acquisition-related expenses			$ 400

[1] The pro forma results for the three months ended March 31, 2012 were adjusted to exclude acquisition-related expenses of approximately $0.4 million incurred in 2012 for the acquisition of 4100-4700 Bohannon Drive, Menlo Park, CA. The pro forma results for the three months ended March 31, 2011 were adjusted to include these expenses.

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