Noncontrolling Interests - Operating Partnership (Details) (USD $)	0 Months Ended		12 Months Ended
	Dec. 12, 2012	Nov. 15, 2011	Dec. 31, 2012	Dec. 31, 2011
Noncontrolling Interests - Operating Partnership
Conversion ratio for common operating partnership units			1
Noncontrolling Interests Operating Partnership
Number of Units (in shares)			45,964,232	45,749,825
Percentage of Total			100.00%	100.00%
Shares of common stock issued related to employee compensation arrangement			205,780
Common Operating Partnership units issued to employees upon their vesting in the incentive unit awards (in shares)			8,627
Preferred Operating Partnership units issued to CoreSite Realty Corporation (in shares)	4,600,000
Common Operating Partnership units redeemed for common stock (in shares)		889,610
Reduction to noncontrolling interests in the Operating Partnership and an increase to common stock and additional paid in capital		$ 13,800,000
Redemption value of the noncontrolling interests			$ 701,300,000
Closing price of the Company's stock (in dollars per share)			$ 27.66
The Company
Noncontrolling Interests Operating Partnership
Number of Units (in shares)			20,610,523	20,404,743
Percentage of Total			44.80%	44.60%
Common units held by third parties
Noncontrolling Interests Operating Partnership
Number of Units (in shares)			25,275,390	25,275,390
Percentage of Total			55.00%	55.20%
Incentive units held by employees
Noncontrolling Interests Operating Partnership
Number of Units (in shares)			78,319	69,692
Percentage of Total			0.20%	0.20%