CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating revenues:
Rental revenue	$ 33,102	$ 29,630
Power revenue	13,529	12,374
Interconnection revenue	6,572	3,655
Tenant reimbursement and other	1,888	1,625
Total operating revenues	55,091	47,284
Operating expenses:
Property operating and maintenance	14,527	14,395
Real estate taxes and insurance	2,220	2,014
Depreciation and amortization	15,949	15,461
Sales and marketing	3,789	2,129
General and administrative	7,003	6,352
Rent	4,793	4,577
Transaction costs	5	122
Total operating expenses	48,286	45,050
Operating income	6,805	2,234
Interest income	2	2
Interest expense	(439)	(1,018)
Income before income taxes	6,368	1,218
Income tax (expense) benefit	(173)	125
Net income	6,195	1,343
Net income attributable to noncontrolling interests	2,262	743
Net income attributable to CoreSite Realty Corporation	3,933	600
Preferred stock dividends	(2,084)
Net income attributable to common shares	$ 1,849	$ 600
Net income per share attributable to common shares:
Basic (in dollars per share)	$ 0.09	$ 0.03
Diluted (in dollars per share)	$ 0.09	$ 0.03
Weighted average common shares outstanding
Basic (in shares)	20,673,896	20,455,875
Diluted (in shares)	21,314,779	20,694,855