Noncontrolling Interests - Operating Partnership (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended	0 Months Ended
Mar. 31, 2015	Dec. 31, 2014	Dec. 12, 2012
Noncontrolling Interests Operating Partnership
Conversion ratio for common operating partnership units	1
Number of Units (in shares)	46,779,136cor_OperatingPartnershipUnitsNumber	46,648,038cor_OperatingPartnershipUnitsNumber
Percentage of Total	100.00%cor_MinorityInterestOwnershipPercentage	100.00%cor_MinorityInterestOwnershipPercentage
Shares of common stock issued related to employee compensation arrangements	131,098
Quarterly distributions will receive by holders of operating partnership units (in dollars per unit)	$ 0.42
Redemption value of the noncontrolling interests	$ 1,234.6
Closing price of the Company's stock (in dollars per share)	$ 48.68us-gaap_SharePrice
Preferred Stock, Dividend Rate, Percentage	7.25%	7.25%
The Company
Noncontrolling Interests Operating Partnership
Number of Units (in shares)	21,418,289	21,287,191
Percentage of Total	45.80%	45.60%
Preferred Operating Partnership units issued to CoreSite Realty Corporation (in shares)			4,600,000
Preferred Stock, Dividend Rate, Percentage			7.25%
Noncontrolling Interests
Noncontrolling Interests Operating Partnership
Number of Units (in shares)	25,360,847	25,360,847
Percentage of Total	54.20%	54.40%

Represents the ownership percentage expressed as a percentage.

No definition available.

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- Definition

Represents the ratio for conversion of Operating Partnership units held by noncontrolling interests into common stock at the option of the entity.

+ References

No definition available.

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- Definition

Represents the number of units held in the Operating Partnership.

+ References

No definition available.

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- Definition

Represents the number of preferred Operating Partnership units issued to the entity.

+ References

No definition available.

+ Details

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- Definition

Per unit of ownership amount of cash distributions declared to unit-holder of a limited partnership (LP).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

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-Section 50

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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- Definition

The percentage rate used to calculate dividend payments on preferred stock.

+ References

No definition available.

+ Details

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- Definition

The aggregate fair value as of the reporting date of all noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. This item includes noncontrolling interest holder's ownership (or holders' ownership) regardless of the type of equity interest (common, preferred, other) including all potential organizational (legal) forms of the investee entity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 480

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- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

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- Definition

Gross number of shares (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP). Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

+ References

No definition available.

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