Subsequent Events (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012 2012 Acquisitons [Member] sqft	Oct. 26, 2012 October Acquisitions [Member] sqft	Oct. 26, 2012 Subsequent Event [Member] sqft	Sep. 30, 2012 Vacant [Member]	Dec. 31, 2011 Vacant [Member]	Sep. 30, 2012 Vacant [Member] Real Estate [Member] sqft	Dec. 31, 2011 Vacant [Member] Real Estate [Member]
Subsequent Event [Line Items]
Number of Real Estate Properties	124	2	126	1	2	1	2
Square feet of acquired property	2,198,877	14,985	2,213,862			3,200
Purchase price of acquired property	$ 235,723	$ 2,258	$ 237,981			$ 1,200

The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityPurchasePrice
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant