Related Party Transactions	9 Months Ended
Related Party Transactions	Sep. 30, 2011
Related Party Transactions [Abstract]
Related Party Transactions	12. Related Party Transactions Prior to the closing of the IPO on September 28, 2010, CoreSite, LLC was engaged to act as the Company’s agent for the purpose of coordinating the activities of the property manager, for leasing and servicing the properties, and for overseeing property build-out activities. Subsequent to our Predecessor’s acquisition of CoreSite, LLC as part of the IPO on September 28, 2010, all related party revenue and expenses incurred in connection with CoreSite, LLC’s activities have been eliminated in consolidation. For the three months and nine months ended September 30, 2010, CoreSite, LLC earned management fees from the Predecessor of $1.3 million and $3.6 million respectively. For the three months and nine months ended September 30, 2010, CoreSite, LLC earned lease commissions from our Predecessor of $0.2 million and $2.8 million, respectively. These commissions are included in deferred leasing costs. For the three and nine months ended September 30, 2010, CoreSite, LLC earned construction management fees from our Predecessor of $0.2 million and $1.2 million, respectively. The construction management fees are included in building improvements and construction in progress. For the three and nine months ended September 30, 2010, CoreSite, LLC was reimbursed for payroll related expenses from our Predecessor of $0.4 million and $1.2 million, respectively. At September 30, 2011 and December 31, 2010, no such fees were payable to CoreSite, LLC. We lease 1,515 net rentable square feet of space at our 12100 Sunrise Valley property to an affiliate of The Carlyle Group. The lease commenced on July 1, 2008 and expires on June 30, 2013. Rental revenue was less than $0.1 million and less than $0.1 million for the three months ended September 30, 2011 and 2010, respectively, and $0.2 million and $0.1 million for the nine months ended September 30, 2011 and 2010, respectively.

The entire disclosure for related party transactions, including the nature of the relationship(s), a description of the transactions, the amount of the transactions, the effects of any change in the method of establishing the terms of the transaction from the previous period, stated interest rate, expiration date, terms and manner of settlement per the agreement with the related party, and amounts due to or from related parties. If the entity and one or more other entities are under common ownership or management control and this control affects the operating results or financial position, disclosure includes the nature of the control relationship even if there are no transactions between the entities. Disclosure may also include the aggregate amount of current and deferred tax expense for each statement of earnings presented where the entity is a member of a group that files a consolidated tax return, the amount of any tax related balances due to or from affiliates as of the date of each statement of financial position presented, the principal provisions of the method by which the consolidated amount of current and deferred tax expense is allocated to the members of the group and the nature and effect of any changes in that method. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(k))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 3A

-Section 04

-Paragraph b

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 57

-Paragraph 1-4

-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.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39678-107864

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 4

-Section 08

-Paragraph k

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39691-107864

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

+ Details