CoreSite Realty 10-Q 24 Jul 15 2015 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Jul. 22, 2015
Document and Entity Information
Entity Registrant Name	CoreSite Realty Corp
Entity Central Index Key	1,490,892
Document Type	10-Q
Document Period End Date	Jun. 30, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		26,531,287
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Investments in real estate:
Land	$ 78,337	$ 78,983
Buildings and improvements	1,012,845	888,966
Total investments in real estate	1,091,182	967,949
Less: Accumulated depreciation and amortization	(247,655)	(215,978)
Net investment in operating properties	843,527	751,971
Construction in progress	106,872	178,599
Net investments in real estate	950,399	930,570
Cash and cash equivalents	7,542	10,662
Accounts and other receivables, net of allowance for doubtful accounts of $132 and $112 as of June 30, 2015 and December 31, 2014, respectively	15,269	10,290
Lease intangibles, net of accumulated amortization of $11,349 and $14,477 as of June 30, 2015 and December 31, 2014, respectively	5,815	7,112
Goodwill	41,191	41,191
Other assets, net	77,569	75,600
Total assets	1,097,785	1,075,425
Liabilities:
Revolving credit facility	102,250	218,500
Senior unsecured term loan	250,000	100,000
Accounts payable and accrued expenses	41,903	42,463
Accrued dividends and distributions	22,467	22,355
Deferred rent payable	8,519	8,985
Acquired below-market lease contracts, net of accumulated amortization of $4,922 and $4,688 as of June 30, 2015 and December 31, 2014, respectively	5,126	5,576
Unearned revenue, prepaid rent and other liabilities	24,734	19,205
Total liabilities	454,999	417,084
Stockholders' equity:
Series A Cumulative Preferred Stock 7.25%, $115,000 liquidation preference ($25.00 per share, $0.01 par value), 4,600,000 shares issued and outstanding as of June 30, 2015 and December 31, 2014	115,000	115,000
Common Stock, par value $0.01, 100,000,000 shares authorized and 26,531,414 and 21,757,366 shares issued and outstanding at June 30, 2015, and December 31, 2014, respectively	259	212
Additional paid-in capital	337,662	275,038
Accumulated other comprehensive loss	(183)	(125)
Distributions in excess of net income	(77,772)	(67,538)
Total stockholders' equity	374,966	322,587
Noncontrolling interests	267,820	335,754
Total equity	642,786	658,341
Total liabilities and equity	$ 1,097,785	$ 1,075,425

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
CONDENSED CONSOLIDATED BALANCE SHEETS
Allowance for doubtful accounts (in dollars)	$ 132	$ 112
Accumulated amortization, lease intangibles (in dollars)	11,349	14,477
Accumulated amortization, acquired below-market lease contracts (in dollars)	$ 4,922	$ 4,688
Series A Cumulative Preferred Stock, dividend rate (as a percent)	7.25%	7.25%
Series A Cumulative Preferred Stock, liquidation preference	$ 115,000	$ 115,000
Series A Cumulative Preferred Stock, liquidation preference (in dollars per share)	$ 25	$ 25
Series A Cumulative Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Series A Cumulative Preferred Stock, shares issued	4,600,000	4,600,000
Series A Cumulative Preferred Stock, shares outstanding	4,600,000	4,600,000
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, shares authorized	100,000,000	100,000,000
Common Stock, shares issued	26,531,414	21,757,366
Common Stock, shares outstanding	26,531,414	21,757,366

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Data center revenue:
Rental revenue	$ 44,824	$ 36,938	$ 86,147	$ 71,837
Power revenue	21,792	16,575	41,461	32,577
Interconnection revenue	10,595	8,591	20,810	16,650
Tenant reimbursement and other	2,276	1,627	3,692	4,383
Office, light-industrial and other revenue	1,969	1,951	4,103	3,966
Total operating revenues	81,456	65,682	156,213	129,413
Operating expenses:
Property operating and maintenance	22,204	18,534	41,984	34,823
Real estate taxes and insurance	3,270	(980)	5,205	1,986
Depreciation and amortization	24,046	19,504	46,862	37,386
Sales and marketing	4,256	3,747	8,038	7,335
General and administrative	7,952	6,732	15,817	14,437
Rent	5,007	5,070	10,250	10,136
Impairment of internal-use software		1,037		1,959
Transaction costs	45	9	45	13
Total operating expenses	66,780	53,653	128,201	108,075
Operating income	14,676	12,029	28,012	21,338
Gain on real estate disposal			36
Interest income	2	2	4	4
Interest expense	(1,730)	(1,415)	(2,995)	(2,588)
Income before income taxes	12,948	10,616	25,057	18,754
Income tax benefit (expense)	(66)	22	(115)	2
Net income	12,882	10,638	24,942	18,756
Net income attributable to noncontrolling interests	5,259	4,670	10,667	7,971
Net income attributable to CoreSite Realty Corporation	7,623	5,968	14,275	10,785
Preferred stock dividends	(2,085)	(2,085)	(4,169)	(4,169)
Net income attributable to common shares	$ 5,538	$ 3,883	$ 10,106	$ 6,616
Net income per share attributable to common shares:
Basic (in dollars per share)	$ 0.23	$ 0.18	$ 0.44	$ 0.31
Diluted (in dollars per share)	$ 0.22	$ 0.18	$ 0.43	$ 0.31
Weighted average common shares outstanding
Basic (in shares)	24,536,583	21,131,077	22,963,111	21,062,299
Diluted (in shares)	25,055,195	21,604,730	23,525,316	21,599,749

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 12,882	$ 10,638	$ 24,942	$ 18,756
Other comprehensive income(loss):
Unrealized gain (loss) on derivative contracts	448	(1,271)	(861)	(754)
Reclassification of other comprehensive income to interest expense	477	337	805	455
Comprehensive income	13,807	9,704	24,886	18,457
Comprehensive income attributable to noncontrolling interests	5,671	4,159	10,547	7,808
Comprehensive income attributable to CoreSite Realty Corporation	$ 8,136	$ 5,545	$ 14,339	$ 10,649

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - 6 months ended Jun. 30, 2015 - USD ($) $ in Thousands	Total Equity	Total Stockholders' Equity	Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Distributions in Excess of Net Income	Noncontrolling Interests	Total
Balance at Dec. 31, 2014	$ 658,341	$ 322,587	$ 115,000	$ 212	$ 275,038	$ (125)	$ (67,538)	$ 335,754	$ 658,341
Balance (in shares) at Dec. 31, 2014				21,757,366
Increase (Decrease) in Stockholders' Equity
Issuance of stock awards, net of forfeitures (in shares)				221,494
Exercise of stock options, net of settlements	(163)	(163)		$ 1	(164)
Exercise of stock options, net of settlements (in shares)				52,554
Share-based compensation	3,644	3,644		$ 1	3,643
Dividends declared on preferred stock	(4,169)	(4,169)					(4,169)
Dividends and distributions	(39,753)	(20,340)					(20,340)	(19,413)
Net income	24,942	14,275					14,275	10,667	24,942
Other comprehensive loss	(56)	64				64		(120)
Redemption of noncontrolling interests		59,068		$ 45	59,145	(122)		(59,068)
Redemption of noncontrolling interests (in shares)				4,500,000
Balance at Jun. 30, 2015	$ 642,786	$ 374,966	$ 115,000	$ 259	$ 337,662	$ (183)	$ (77,772)	$ 267,820	$ 642,786
Balance (in shares) at Jun. 30, 2015				26,531,414

CONDENSED CONSOLIDATED STATEME7

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 24,942	$ 18,756
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	46,862	37,386
Amortization of Intangible Assets	(258)	(182)
Amortization of deferred financing costs	586	1,029
Gain on real estate disposal	(36)
Share-based compensation	3,361	3,248
Bad debt expense	168	529
Changes in operating assets and liabilities:
Accounts receivable	(5,148)	(465)
Deferred rent receivable	(2,915)	(1,330)
Deferred leasing costs	(7,861)	(3,470)
Other assets	(2,408)	385
Accounts payable and accrued expenses	(1,023)	(6,430)
Unearned revenue , prepaid rent and other liabilities	5,015	5,294
Deferred rent payable	(466)	(245)
Net cash provided by operating activities	60,819	54,505
CASH FLOWS FROM INVESTING ACTIVITIES
Tenant improvements	(3,671)	(4,487)
Real estate improvements	(50,238)	(50,899)
Procees from real estate disposal	2,399
Net cash used in investing activities	(51,510)	(55,386)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from exercise of stock options	667	407
Proceeds from revolving credit facility	37,750	43,500
Payments on revolving credit facility	(154,000)	(41,000)
Proceeds from senior unsecured term loan	150,000	100,000
Repayments of mortgage loans payable		(58,250)
Payments of loan fees and costs	(2,207)	(1,000)
Payments to net settle equity awards	(830)
Dividends and distributions	(43,809)	(36,957)
Net cash provided by financing activities	(12,429)	6,700
Net change in cash and cash equivalents	(3,120)	5,819
Cash and cash equivalents, beginning of period	10,662	5,313
Cash and cash equivalents, end of period	7,542	11,132
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for interest, net of capitalized amounts	2,617	1,810
NON-CASH INVESTING AND FINANCING ACTIVITY
Construction costs payable capitalized to real estate	14,439	26,700
Accrual of dividends and distributions	$ 22,467	$ 18,772

Organization and Description of

Organization and Description of Business	6 Months Ended
	Jun. 30, 2015
Organization and Description of Business
Organization and Description of Business	1. Organization and Description of Business CoreSite Realty Corporation (the “Company,” “we,” or “our”) was organized in the state of Maryland on February 17, 2010, and is a fully-integrated, self-administered, and self-managed real estate investment trust (“REIT”). Through our controlling interest in CoreSite, L.P. (our “Operating Partnership”), we are engaged in the business of owning, acquiring, constructing and operating data centers. As of June 30, 2015, the Company owns a 55.5% common interest in our Operating Partnership and affiliates of The Carlyle Group and others own a 44.5% interest in our Operating Partnership. See additional discussion in Note 8.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2015
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Principles of Consolidation and Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared by our management in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and in compliance with the rules and regulations of the United States Securities and Exchange Commission. Accordingly, these unaudited condensed consolidated financial statements do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of our management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. The results of operations for six months ended June 30, 2015, are not necessarily indicative of the expected results for the year ending December 31, 2015. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2014. Intercompany balances and transactions have been eliminated upon consolidation. In February 2015, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2015-02, Amendments to the Consolidation Analysis , which amends the current consolidation guidance. ASU 2015-02 is effective for annual and interim periods beginning after December 15, 2015, with early adoption permitted. The standard permits the use of either modified retrospective or cumulative effect transition method. We have not elected early adoption and we are currently evaluating the impact of the provisions of ASU 2015-02 on our consolidation policies as well as the transition method to be used to implement ASU 2015-02. Use of Estimates The preparation of these unaudited condensed consolidated financial statements in conformity with GAAP requires our management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingencies at the date of the unaudited condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. We evaluate our estimates, including those related to assessing the carrying values of our real estate properties, goodwill, accrued liabilities and performance-based equity compensation plans. We base our estimates on historical experience, current market conditions, and various other assumptions that we believe to be reasonable under the circumstances. Actual results may vary from those estimates and those estimates could vary under different assumptions or conditions. Adjustments and Reclassifications Certain immaterial amounts included in the condensed consolidated financial statements for 2014 have been reclassified to conform to the 2015 financial statement presentation. Investments in Real Estate Real estate investments are carried at cost less accumulated depreciation and amortization. The cost of real estate includes the purchase price of property and leasehold improvements. Expenditures for maintenance and repairs are expensed as incurred. Significant renovations and betterments that extend the economic useful lives of assets are capitalized. During land development and construction periods, we capitalize construction costs, legal fees, financing costs, real estate taxes and insurance and internal costs of personnel performing development, if such costs are incremental and identifiable to a specific development project. Capitalization of costs begins upon commencement of development efforts and ceases when the property is ready for its intended use and held available for occupancy. Interest is capitalized during the period of development based upon applying the weighted-average borrowing rate to the actual development costs expended. Capitalized interest costs were $1.0 million and $1.0 million for the three months ended June 30, 2015, and 2014, respectively, and $2.3 million and $2.2 million for the six months ended June 30, 2015, and 2014, respectively. Depreciation and amortization are calculated using the straight-line method over the following useful lives of the assets: Buildings 27 to 40 years Building improvements 1 to 10 years Leasehold improvements The shorter of the lease term or useful life of the asset Depreciation expense was $19.2 million and $15.9 million for the three months ended June 30, 2015, and 2014, respectively, and $37.1 million and $31.0 million for the six months ended June 30, 2015, and 2014, respectively. Acquisition of Investment in Real Estate Purchase accounting is applied to the assets and liabilities related to all real estate investments acquired. The fair value of the real estate acquired is allocated to the acquired tangible assets, consisting primarily of land, building and building improvements, and identified intangible assets and liabilities, consisting of the value of above-market and below-market leases, value of in-place leases and the value of customer relationships. The fair value of the land and building of an acquired property is determined by valuing the property as if it were vacant, and the “as-if-vacant” fair value is then allocated to land and building based on management’s determination of the fair values of these assets. Management determines the as-if-vacant fair value of a property using methods similar to those used by independent appraisers. Factors considered by management in performing these analyses include an estimate of carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases. The fair value of intangibles related to in-place leases includes the value of lease intangibles for above-market and below-market leases, lease origination costs, and customer relationships, determined on a lease-by-lease basis. Above-market and below-market leases are valued based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) management’s estimate of fair market lease rates for the corresponding in-place leases, measured over a period equal to the remaining noncancelable term of the lease and, for below-market leases, over a period equal to the initial term plus any below-market fixed rate renewal periods. Lease origination costs include estimates of costs avoided associated with leasing the property, including tenant allowances and improvements and leasing commissions. Customer relationship intangibles relate to the additional revenue opportunities expected to be generated through interconnection services and utility services to be provided to the in-place lease tenants. The capitalized values for above and below-market lease intangibles, lease origination costs, and customer relationships are amortized over the term of the underlying leases or the expected customer relationship. Amortization related to above-market and below-market leases where the Company is the lessor is recorded as either a reduction of or an increase to rental income, amortization related to above-market and below-market leases where the Company is the lessee is recorded as either a reduction of or an increase to rent expense. If a lease is terminated prior to its stated expiration, all unamortized amounts relating to that lease are written off. The carrying value of intangible assets is reviewed for impairment in connection with its respective asset group whenever events or changes in circumstances indicate that the asset group may not be recoverable. An impairment loss is recognized if the carrying amount of the asset group is not recoverable and its carrying amount exceeds its estimated fair value. No impairment loss related to these intangible assets was recognized for either the three or six months ended June 30, 2015, or 2014. The excess of the cost of an acquired business over the net of the amounts assigned to assets acquired (including identified intangible assets) and liabilities assumed is recorded as goodwill. As of June 30, 2015, and December 31, 2014, we had approximately $41.2 million of goodwill at each date. The Company’s goodwill has an indeterminate life and is not amortized, but is tested for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the asset might be impaired. No impairment loss was recognized for either the three or six months ended June 30, 2015, or 2014. Cash and Cash Equivalents Cash and cash equivalents include all non-restricted cash held in financial institutions and other non-restricted highly liquid short-term investments with original maturities at acquisition of three months or less. Deferred Costs Deferred leasing costs include commissions paid to third parties, including leasing agents, and internal sales commissions paid to employees for successful execution of lease agreements. These commissions and other direct and incremental costs incurred to obtain new customer leases are capitalized and amortized over the terms of the related leases using the straight-line method. If a lease terminates prior to the expiration of its initial term, any unamortized deferred costs related to the lease are written off to amortization expense. Deferred leasing costs are included within other assets in the condensed consolidated balance sheets and consisted of the following, net of amortization, as of June 30, 2015, and December 31, 2014 (in thousands): June 30, December 31, 2015 2014 Internal sales commissions $ $ Third party commissions External legal counsel Total $ $ Deferred financing costs include costs incurred in connection with obtaining debt and extending existing debt. These financing costs are capitalized and amortized on a straight-line basis, which approximates the effective-interest method, over the term of the loan and the amortization is included as a component of interest expense. In March 2015, the FASB issued ASU 2015-03, Simplifying the Presentation of Debt Issuance Costs , which amends the current imputation of interest guidance. ASU 2015-03 is effective for annual and interim periods beginning after December 15, 2015, with early adoption permitted. We have not elected early adoption and we are currently evaluating the impact of the provisions of ASU 2015-03 on our balance sheet presentation. Recoverability of Long-Lived Assets We review our long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Impairment is recognized when estimated expected future cash flows (undiscounted and without interest charges) are less than the carrying amount of the assets. The estimation of expected future net cash flows is inherently uncertain and relies, to a considerable extent, on assumptions regarding current and future economics and market conditions and the availability of capital. If, in future periods, there are changes in the estimates or assumptions incorporated into the impairment review analysis, the changes could result in an adjustment to the carrying amount of the long-lived assets. To the extent that impairment has occurred, the excess of the carrying amount of long-lived assets over its estimated fair value would be recognized as an impairment loss charged to net income. For the three and six months ended June 30, 2015, and 2014, no impairment of long-lived assets was recognized. Derivative Instruments and Hedging Activities We reflect all derivative instruments at fair value as either assets or liabilities on the condensed consolidated balance sheets. For those derivative instruments that are designated and qualify as hedging instruments, we record the effective portion of the gain or loss on the hedge instruments as a component of accumulated other comprehensive income or loss. Any ineffective portion of a derivative’s change in fair value is immediately recognized within net income. For derivatives that do not meet the criteria for hedge accounting, changes in fair value are immediately recognized within net income. See additional discussion in Note 6. Internal-Use Software We recognize internal-use software development costs based on the development stage of the project and nature of the cost. Internal and external costs incurred during the preliminary project stage are expensed as they are incurred. Internal and external costs incurred to develop internal-use software during the application development stage are capitalized. Internal and external training costs and maintenance costs during the post-implementation-operation stage are expensed as incurred. Completed projects are placed into service and amortized over the estimated useful life of the software. Impairment recognized, related to internal use software, in the condensed consolidated statements of operations during the three months ended June 30, 2015, and 2014, was zero and $1.0 million, respectively, and impairment recognized during the six months ended June 30, 2015, and 2014, was zero and $2.0 million, respectively. In April 2015, the FASB issued ASU 2015-05, Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement , which provides explicit guidance to help companies evaluate the accounting for fees paid by a customer in a cloud computing arrangement. ASU 2015-05 is effective for annual and interim beginning after December 15, 2015, with early adoption permitted. We have not elected early adoption and we are currently evaluating the impact of the provisions of ASU 2015-05 on our consolidated financial statements. Revenue Recognition All customer leases are classified as operating leases and minimum rents are recognized on a straight-line basis over the noncancelable term of the agreements. The excess of rents recognized over amounts contractually due pursuant to the underlying leases are included in deferred rent receivable. If a lease terminates prior to its stated expiration, the deferred rent receivable relating to that lease is written off as a reduction of rental revenue. When arrangements include multiple elements, the revenue associated with separate elements is allocated based on the relative fair values of those elements. The revenue associated with each element is then recognized as earned. Interconnection services and additional space services are considered as separate earnings processes that are provided and completed on a month-to-month basis and revenue is recognized in the period that services are performed. Customer set-up charges and utility installation fees are initially deferred and recognized over the term of the arrangement as revenue. Tenant reimbursements for real estate taxes, common area maintenance, and other recoverable costs are recognized as revenue in the period that the related expenses are incurred. Above-market and below-market lease intangibles that were acquired are amortized on a straight-line basis as decreases and increases, respectively, to rental revenue over the remaining noncancelable term of the underlying leases. For each of the three month periods ended June 30, 2015, and 2014, the net effect of amortization of acquired above-market and below-market leases resulted in an increase to rental revenue of $0.1 million. For the six months ended June 30, 2015, and 2014, the net effect of amortization of acquired above-market and below-market leases resulted in an increase to rental revenue of $0.3 million and $0.2 million, respectively. A provision for uncollectible accounts is recorded if a receivable balance relating to contractual rent, rent recorded on a straight-line basis, tenant reimbursements or other billed amounts is considered by management to be uncollectible. At June 30, 2015, and December 31, 2014, the allowance for doubtful accounts totaled $0.1 million and $0.1 million, respectively. In May 2014, the FASB issued guidance codified in Accounting Standards Codification (“ASC”) 606, Revenue Recognition — Revenue from Contracts with Customers , which amends the guidance in former ASC 605, Revenue Recognition . The standard is effective for interim and annual reporting periods beginning after December 15, 2016. The standard permits the use of either the retrospective or cumulative effect transition method. We are currently evaluating the impact of the provisions of ASC 606 on our revenue recognition policies as well as the transition method to be used to implement this guidance. Share-Based Compensation We account for share-based compensation using the fair value method of accounting. The estimated fair value of the stock options granted by us is calculated based on the Black-Scholes option-pricing model. The fair value of restricted share-based and Operating Partnership unit compensation is based on the market value of our common stock on the date of the grant. The fair value of performance share awards, which have a market condition, is based on a Monte Carlo simulation. The fair value for all share-based compensation is amortized on a straight-line basis over the vesting period. Asset Retirement and Environmental Remediation Obligations We record accruals for estimated asset retirement and environmental remediation obligations. The obligations relate primarily to the removal of asbestos and contaminated soil during development of properties as well as the estimated equipment removal costs upon termination of a certain lease where we are the lessee. At both June 30, 2015, and December 31, 2014, the amount included in unearned revenue, prepaid rent and other liabilities on the condensed consolidated balance sheets was approximately $2.3 million. Income Taxes We elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the “Code”), commencing with our taxable year ended December 31, 2010. To qualify as a REIT, we are required to distribute at least 90% of our taxable income to our stockholders and meet various other requirements imposed by the Code relating to such matters as operating results, asset holdings, distribution levels and diversity of stock ownership. Provided we qualify for taxation as a REIT, we generally are not subject to corporate level federal income tax on the earnings distributed currently to our stockholders. If we fail to qualify as a REIT in any taxable year, and are unable to avail ourselves of certain savings provisions set forth in the Code, all of our taxable income would be subject to federal income tax at regular corporate rates, including any applicable alternative minimum tax. To maintain REIT status, we must distribute a minimum of 90% of our taxable income. However, it is our policy and intent, subject to change, to distribute 100% of our taxable income and therefore no provision is required in the accompanying condensed consolidated financial statements for federal income taxes with regards to activities of the REIT and its subsidiary pass-through entities. The allocable share of taxable income is included in the income tax returns of its stockholders. The Company is subject to the statutory requirements of the locations in which it conducts business. State and local income taxes are accrued as deemed required in the best judgment of management based on analysis and interpretation of respective tax laws. We have elected to treat certain subsidiaries as taxable REIT subsidiaries (“TRS”). Certain activities that we undertake must be conducted by a TRS, such as services for our tenants that could be considered otherwise impermissible for us to perform and holding assets that we cannot hold directly. A TRS is subject to corporate level federal and state income taxes. Deferred income taxes are recognized in certain taxable entities. Deferred income tax generally is a function of the period’s temporary differences (items that are treated differently for tax purposes than for financial reporting purposes), the utilization of tax net operating losses generated in prior years that previously had been recognized as deferred income tax assets and the reversal of any previously recorded deferred income tax liabilities. A valuation allowance for deferred income tax assets is provided if we believe all or some portion of the deferred income tax asset may more likely than not be not realized. Any increase or decrease in the valuation allowance resulting from a change in circumstances that causes a change in the estimated realizability of the related deferred income tax asset is included in deferred tax expense. As of June 30, 2015, and December 31, 2014, the gross deferred income taxes were not material. We currently have no liabilities for uncertain income tax positions. The earliest tax year for which we are subject to examination is 2011. Concentration of Credit Risks Our cash and cash equivalents are maintained in various financial institutions, which, at times, may exceed federally insured limits. We have not experienced any losses in such accounts, and management believes that the Company is not exposed to any significant credit risk in this area. We have no off-balance sheet concentrations of credit risk, such as foreign exchange contracts, option contracts, or foreign currency hedging arrangements. Segment Information We manage our business as one reportable segment consisting of investments in data centers located in the United States. Although we provide services in several markets, these operations have been aggregated into one reportable segment based on the similar economic characteristics amongst all markets, including the nature of the services provided and the type of customers purchasing these services.

Investment in Real Estate

Investment in Real Estate	6 Months Ended
	Jun. 30, 2015
Investment in Real Estate
Investment in Real Estate	3. Investment in Real Estate The following is a summary of the properties owned or leased at June 30, 2015 (in thousands): Buildings and Construction Property Name Location Land Improvements in Progress Total Cost SV1 San Jose, CA $ $ $ $ SV2 Milpitas, CA SV3 Santa Clara, CA SV4 Santa Clara, CA SV5 Santa Clara, CA — SV6 Santa Clara, CA — — Santa Clara Campus(1) Santa Clara, CA BO1 Somerville, MA NY1* New York, NY — NY2 Secaucus, NJ VA1 Reston, VA VA2 Reston, VA DC1* Washington, DC — CH1 Chicago, IL LA1* Los Angeles, CA — LA2 Los Angeles, CA MI1 Miami, FL DE1* Denver, CO — DE2* Denver, CO — — Total $ $ $ $ * Indicates properties in which we hold a leasehold interest. (1) This campus includes office and light-industrial buildings and land held for development in Santa Clara, California.

Other Assets

Other Assets	6 Months Ended
	Jun. 30, 2015
Other Assets
Other Assets	4. Other Assets Our other assets consisted of the following, net of amortization and depreciation, if applicable, as of June 30, 2015, and December 31, 2014 (in thousands): June 30, December 31, 2015 2014 Deferred leasing costs $ $ Deferred rent receivable Corporate furniture, fixtures and equipment Internal-use software Deferred financing costs Prepaid expenses Other Total $ $

Debt

Debt	6 Months Ended
	Jun. 30, 2015
Debt
Debt	5. Debt A summary of outstanding indebtedness as of June 30, 2015, and December 31, 2014, is as follows (in thousands): Maturity June 30, December 31, Interest Rate Date 2015 2014 Revolving credit facility 1.73% and 2.17% at June 30, 2015, and December 31, 2014, respectively June 24, 2019 $ $ 2019 Senior unsecured term loan(1) 3.23% at June 30, 2015, and at December 31, 2014 January 31, 2019 2020 Senior unsecured term loan(2) 2.31% at June 30, 2015 June 24, 2020 — Total principal outstanding $ $ (1) The Operating Partnership elected to swap the variable interest rate associated with the 2019 Senior unsecured term loan to a fixed rate of approximately 3.23% per annum at our current leverage ratio. (2) The Operating Partnership elected to swap the variable interest rate associated with $75 million, or 50%, of the principal amount of the 2020 Senior unsecured term loan to a fixed rate of approximately 2.93% per annum at our current leverage ratio. The interest rate on the remaining $75 million of the 2020 Senior unsecured term loan is based on LIBOR plus the applicable spread. The effective interest rate as of June 30, 2015, is 2.31%. Revolving Credit Facility On June 24, 2015, our Operating Partnership and certain subsidiary co-borrowers entered into a third amended and restated senior unsecured revolving credit facility (as amended, the “Credit Agreement”) with a group of lenders for which KeyBank National Association acts as the administrative agent. The Credit Agreement amends the Operating Partnership’s second amended and restated unsecured revolving credit facility, dated January 3, 2013 (as amended, the “Prior Facility”). The Credit Agreement maturity date is June 24, 2019, with a one-time extension option, which, if exercised, would extend the maturity date to June 24, 2020. The exercise of the extension option is subject to the payment of an extension fee equal to 10 basis points of the total commitment under the Credit Agreement at initial maturity and certain other customary conditions. The Credit Agreement increases the commitment from the Prior Facility of $405 million to $500 million, providing for a $350 million revolving credit facility and a $150 million unsecured term loan. See “2020 Senior Unsecured Term loan” below for a discussion of the $150 million term loan. The Credit Agreement contains an accordion feature, which allows our Operating Partnership to increase the total commitment from $500 million to $700 million, under specified circumstances. Under the Credit Agreement, borrowings under the revolving credit facility bear interest at a variable rate per annum equal to either (i) LIBOR plus 155 basis points to 225 basis points, or (ii) a base rate plus 55 basis points to 125 basis points, each depending on our Operating Partnership’s leverage ratio. At June 30, 2015, the Operating Partnership’s leverage ratio was 17.9% and the interest rate was LIBOR plus 155 basis points. The total amount available for borrowings under the revolving credit facility is subject to the lesser of $350.0 million or the availability calculated based on our unencumbered asset pool. As of June 30, 2015, the borrowing capacity was $350.0 million. As of June 30, 2015, $102.3 million was borrowed and outstanding, $6.3 million was outstanding under letters of credit and $241.4 million remained available for us to borrow under the Credit Agreement. Our ability to borrow under the Credit Agreement is subject to ongoing compliance with a number of financial covenants and other customary restrictive covenants, including, among others: · a maximum leverage ratio (defined as total consolidated indebtedness to total gross asset value) of 60%, which, as of June 30, 2015, was 17.9%; · a maximum secured debt ratio (defined as total consolidated secured debt to total gross asset value) of 40%, which, as of June 30, 2015, was 0%; · a minimum fixed charge coverage ratio (defined as adjusted consolidated earnings before interest, taxes, depreciation and amortization to consolidated fixed charges) of 1.70 to 1.00, which, as of June 30, 2015, was 8.4 to 1.00; and · a maximum unhedged variable rate debt ratio (defined as unhedged variable rate indebtedness to gross asset value) of 30%, which, as of June 30, 2015, was 8.3%. As of June 30, 2015, we were in compliance with all of the covenants under the Credit Agreement. 2020 Senior Unsecured Term Loan On June 24, 2015, in connection with the Credit Agreement, our Operating Partnership and certain subsidiaries entered into a $150 million senior unsecured term loan (the “2020 Term Loan”). The 2020 Term Loan has a five-year term maturing on June 24, 2020. The 2020 Term Loan ranks pari passu with our Credit Agreement and contains the same financial covenants and other customary restrictive covenants. As of June 30, 2015, we were in compliance with all of the covenants under the 2020 Term Loan. The borrowings under the 2020 Term Loan bear interest at a variable rate per annum equal to either (i) LIBOR plus 150 basis points to 220 basis points, or (ii) a base rate plus 50 basis points to 120 basis points, each depending on our Operating Partnership’s leverage ratio. At June 30, 2015, the Operating Partnership’s leverage ratio was 17.9% and the interest rate was LIBOR plus 150 basis points. 2019 Senior Unsecured Term Loan On January 31, 2014, our Operating Partnership and certain subsidiaries entered into a $100 million senior unsecured term loan (as amended, the “2019 Term Loan”). The 2019 Term Loan has a five-year term and contains an accordion feature, which allows our Operating Partnership to increase the total commitments by $100 million, to $200 million, under specified circumstances. The 2019 Term Loan ranks pari passu with our Credit Agreement and contains the same financial covenants and other customary restrictive covenants. As of June 30, 2015, we were in compliance with all of the covenants under the 2019 Term Loan. The borrowings under the 2019 Term Loan bear interest at a variable rate per annum equal to either (i) LIBOR plus 175 basis points to 265 basis points, or (ii) a base rate plus 75 basis points to 165 basis points, each depending on our Operating Partnership’s leverage ratio. At June 30, 2015, the Operating Partnership’s leverage ratio was 17.9% and the interest rate was LIBOR plus 175 basis points. Debt Maturities The following table summarizes the amount of our outstanding debt as of June 30, 2015, when such debt currently becomes due (in thousands): Year Ending December 31, Remainder of 2015 $ — 2016 — 2017 — 2018 — 2019 2020 Total $

Derivatives and Hedging Activit

Derivatives and Hedging Activities	6 Months Ended
	Jun. 30, 2015
Derivatives and Hedging Activities
Derivatives and Hedging Activities	6. Derivatives and Hedging Activities On April 9, 2015, we entered into a $75 million forward starting five-year interest rate swap agreement, effective May 5, 2015, to protect against adverse fluctuation in interest rates. The swap reduces our exposure to variability in cash flows relating to interest payments on $75 million of one-month LIBOR variable rate debt and effectively fixed the interest rate at approximately 2.93% per annum. Also, on February 3, 2014, we entered into a $100 million five-year interest rate swap agreement that effectively fixes the interest rate at approximately 3.23% per annum. Both interest rate swap agreements were designated for hedge accounting. Risk Management Objective of Using Derivatives We are exposed to certain risks arising from both our business operations and economic conditions. We principally manage our exposures to a wide variety of business and operational risks through management of our core business activities. We manage economic risks, including interest rate, liquidity, and credit risk primarily by managing the amount, sources, and duration of our debt funding and the use of derivative financial instruments. Specifically, we enter into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known or uncertain cash amounts, the value of which are determined by interest rates. Our derivative financial instruments are used to manage differences in the amount, timing, and duration of our known or expected cash receipts and our known or expected cash payments principally related to our investments and borrowings. Cash Flow Hedges of Interest Rate Risk Our objectives in using interest rate derivatives are to reduce variability in interest expense and to manage our exposure to adverse interest rate movements. To accomplish this objective, we primarily use interest rate swaps as part of our interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable amounts from a counterparty in exchange for the Company making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income or loss on the condensed consolidated balance sheets and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. The amounts recorded in other comprehensive income related to the unrealized gain or loss on derivative contracts were a gain of $0.4 million and a loss of $1.3 million for the three months ended June 30, 2015, and 2014, respectively, and a loss of $0.9 million and $0.8 million for the six months ended June 30, 2015, and 2014, respectively. The amounts reclassified out of other comprehensive income into interest expense on the condensed consolidated statements of operations were $0.5 million and $0.3 million for the three months ended June 30, 2015, and 2014, respectively, and $0.8 million and $0.5 million for the six months ended June 30, 2015, and 2014, respectively. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings. During the three and six months ended June 30, 2015, and 2014, we did not record any amount in earnings related to derivatives as there was no hedge ineffectiveness. Amounts reported in accumulated other comprehensive loss related to derivatives will be reclassified to interest expense as interest payments are made on our variable-rate debt. During the subsequent twelve months, beginning July 1, 2015, we estimate that $1.9 million will be reclassified as an increase to interest expense. Derivatives are recorded at fair value in our condensed consolidated balance sheets in other assets and other liabilities, as applicable. We do not net our derivative position by counterparty for purposes of balance sheet presentation and disclosure. We had $0.8 million and $0.3 million in derivative liabilities recognized in unearned revenue, prepaid rent and other liabilities in our condensed consolidated balance sheet as of June 30, 2015, and December 31, 2014, respectively. We also had a $0.5 million derivative asset recognized in other assets in our condensed consolidated balance sheet as of June 30, 2015. We had no derivative assets recognized in other assets in our condensed consolidated balance sheet as of December 31, 2014.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2015
Stockholders' Equity
Stockholders' Equity	7. Stockholders’ Equity We paid the following dividends per share on our Series A cumulative preferred stock and common stock during the six months ended June 30, 2015: Declaration Date Record Date Payment Date Preferred Stock Common Stock March 12, 2015 March 31, 2015 April 15, 2015 $ (1) $ May 21, 2015 June 30, 2015 July 15, 2015 (2) $ $ (1) Dividend covers the period from January 15, 2015, to April 14, 2015. (2) Dividend covers the period from April 15, 2015, to July 14, 2015.

Noncontrolling Interests - Oper

Noncontrolling Interests - Operating Partnership	6 Months Ended
	Jun. 30, 2015
Noncontrolling Interests - Operating Partnership
Noncontrolling Interests - Operating Partnership	8. Noncontrolling Interests — Operating Partnership Noncontrolling interests represent the limited partnership interests in the Operating Partnership held by individuals and entities other than CoreSite Realty Corporation. The current holders of common Operating Partnership units are eligible to have the common Operating Partnership units redeemed for cash or common stock on a one-for-one basis, at our option. In connection with the issuance of our 7.25% Series A cumulative redeemable preferred stock on December 12, 2012, the Operating Partnership issued 4,600,000 7.25% Series A Cumulative redeemable preferred Operating Partnership units to us. Preferred Operating Partnership units rank senior to the common Operating Partnership units held by both us and noncontrolling interests. The following table shows the ownership interests in the Operating Partnership as of June 30, 2015, and December 31, 2014: June 30, 2015 December 31, 2014 Number of Units Percentage of Total Number of Units Percentage of Total CoreSite Realty Corporation % % Noncontrolling interests % % Total % % For each share of common stock issued by us, the Operating Partnership issues to us an equivalent common Operating Partnership unit. During the six months ended June 30, 2015, we issued 203,670 shares of common stock related to employee compensation arrangements and therefore an equivalent number of common Operating Partnership units were issued to us by the Operating Partnership. Holders of common Operating Partnership units of record as of June 30, 2015, received quarterly distributions of $0.42 per unit, payable in correlation with declared dividends on common stock. On May 1, 2015, 4,500,000 common Operating Partnership units held by third parties were redeemed for shares of our common stock in connection with the offer and sale of 4,500,000 shares of our common stock by The Carlyle Group. This redemption was recorded as a $59.1 million reduction to noncontrolling interests in the Operating Partnership and an increase to common stock and additional paid-in capital. The redemption value of the noncontrolling interests at June 30, 2015, was $947.9 million based on the closing price of the Company’s common stock of $45.44 on that date.

Equity Incentive Plan

Equity Incentive Plan	6 Months Ended
	Jun. 30, 2015
Equity Incentive Plan
Equity Incentive Plan	9. Equity Incentive Plan Our Board of Directors has adopted and, with the approval of our stockholders, amended the 2010 Equity Incentive Plan (as amended, the “2010 Plan”). The 2010 Plan is administered by the Compensation Committee of the Board of Directors. Awards issuable under the 2010 Plan include common stock, stock options, restricted stock, stock appreciation rights, dividend equivalents, Operating Partnership units and other incentive awards. We have reserved a total of 6,000,000 shares of our common stock for issuance pursuant to the 2010 Plan, which may be adjusted for changes in our capitalization and certain corporate transactions. To the extent that an award expires, terminates or lapses then any unexercised shares subject to the award will be available for future grant or sale under the 2010 Plan. Shares of restricted stock which are forfeited or repurchased by us pursuant to the 2010 Plan may again be awarded under the 2010 Plan. The payment of dividend equivalents in cash in conjunction with any outstanding awards will not be counted against the shares available for issuance under the 2010 Plan. As of June 30, 2015, 3,341,238 shares of our common stock were available for issuance pursuant to the 2010 Plan. Stock Options Stock option awards are granted with an exercise price equal to the closing market price of the Company’s common stock on the date of grant. The fair value of each option granted under the 2010 Plan is estimated on the date of grant using the Black-Scholes option-pricing model. The fair values are amortized on a straight-line basis over the vesting periods. The following table sets forth stock option activity under the 2010 Plan for the three months ended June 30, 2015: Number of Shares Subject to Options Weighted- Average Exercise Price Options outstanding, December 31, 2014 $ Granted — — Exercised ) Forfeited ) Expired ) Options outstanding, June 30, 2015 $ The following table sets forth the number of shares subject to options that are unvested as of June 30, 2015, and the fair value of these options at the grant date: Number of Shares Subject to Options Weighted- Average Fair Value at Grant Date Unvested balance, December 31, 2014 $ Granted — — Forfeited ) Vested ) Unvested balance, June 30, 2015 $ As of June 30, 2015, total unearned compensation on options was approximately $0.8 million, and the weighted-average vesting period was 1.4 years. Restricted Awards and Units During the six months ended June 30, 2015, we granted 176,582 shares of restricted stock which had a fair value of $8.4 million as of the date of grant. Also during the six months ended June 30, 2015, we issued 7,128 restricted stock units, or RSUs. The principal difference between these instruments is that RSUs are not shares of our common stock and do not have any of the rights or privileges thereof, including voting rights. On the applicable vesting date, the holder of an RSU becomes entitled to a share of common stock. The restricted stock awards are amortized on a straight-line basis to expense over the vesting period. The following table sets forth the number of unvested restricted stock and RSU awards and the weighted-average fair value of these awards at the date of grant: Restricted Awards Weighted- Average Fair Value at Grant Date Unvested balance, December 31, 2014 $ Granted Forfeited ) Vested ) Unvested balance, June 30, 2015 $ As of June 30, 2015, total unearned compensation on restricted awards was approximately $13.3 million, and the weighted-average vesting period was 2.7 years. Performance Stock Awards We grant long-term incentives to members of management in the form of performance-based restricted stock awards (“PSAs”) under the 2010 Plan. The number of PSAs earned is based on our achievement of relative total shareholder return (“TSR”) measured versus the MSCI US REIT Index over a three-year performance period, and the number of shares earned under the PSAs may range from 0% to 150% for 2014 grants and from 25% to 175% for 2015 grants. The PSAs are earned as follows: (i) 20% of the PSAs are eligible to be earned upon TSR achievement in year one of the performance period, (ii) 20% of the PSAs are eligible to be earned upon TSR achievement in year two of the performance period, (iii) 20% of the PSAs are eligible to be earned upon TSR achievement in year three of the performance period, and (iv) 40% of the PSAs are eligible to be earned upon a cumulative TSR achievement over the three-year performance period. The PSAs have a service condition and will be released at the end of the three-year performance period, to the extent earned, provided that the holder continues to be employed by the Company at the end of the three-year performance period. Holders of the PSAs are entitled to dividends on the PSAs, which will be accrued and paid in cash at the end of the three-year performance period. The PSAs initially are granted and issued at the highest target amount and thereafter are forfeited to the extent vesting conditions are not met. On March 4, 2014, we granted 91,335 PSAs equal to 150% of the target amount, with an aggregate value of $1.6 million on the grant date. The PSAs, in addition to a service condition, are subject to our performance versus the MSCI US REIT Index, which is a market condition and impacts the number of shares that ultimately vests. Upon evaluating the results of the market condition, the final number of shares is determined and such shares vest based on satisfaction of the service condition. The PSAs are amortized on a straight-line basis over the vesting period. During the six months ended June 30, 2015, 3,782 of the PSAs granted in March 2014 were forfeited due to termination of service and 6,872 PSAs were not achieved due to performance against the MSCI REIT Index correlating to less than 150% of the target amount during the first year of the performance period. On March 3, 2015, we granted 78,553 PSAs, equal to 175% of the target amount, with an aggregate value of $2.7 million on the grant date. The PSAs, in addition to a service condition, are subject to our performance versus the MSCI US REIT Index which is a market condition and impacts the number of shares that ultimately vests. Upon evaluating the results of the market condition, the final number of shares is determined and such shares vest based on satisfaction of the service condition. The PSAs are amortized on a straight-line basis over the vesting period. During the six months ended June 30, 2015, 3,637 of the PSAs granted in March 2015 were forfeited due to termination of service. As of June 30, 2015, total unearned compensation on PSAs was approximately $3.1 million, and the weighted-average vesting period was 2.5 years. The fair value of each PSA award is estimated on the date of grant using a Monte Carlo simulation. The simulation requires assumptions for expected volatility, risk-free rate of return, and dividend yield. The following table summarizes the assumptions used to value the PSAs granted during the six months ended June 30, 2015, and 2014. Six Months Ended June 30, 2015 2014 Expected term (in years) Expected volatility % % Expected annual dividend — — Risk-free rate % %

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2015
Earnings Per Share
Earnings Per Share	10. Earnings Per Share Basic income per share is calculated by dividing the net income attributable to common shares by the weighted-average number of common shares outstanding during the period. Diluted income per share adjusts basic income per share for the effects of potentially dilutive common shares, if the effect is not antidilutive. Potentially dilutive common stock consist of shares issuable under the 2010 Plan. The following is a summary of basic and diluted income per share (in thousands, except share and per share amounts): Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Net income attributable to common shares $ $ $ $ Weighted-average common shares outstanding - basic Effect of potentially dilutive common shares: Stock options Unvested awards Weighted-average common shares outstanding - diluted Net income per share attributable to common shares Basic $ $ $ $ Diluted $ $ $ $ In the calculations above, we have excluded weighted-average potentially dilutive securities of 43,013 and 165,552 for the three months ended June 30, 2015, and 2014, respectively, and 141,081 and 202,422 for the six months ended June 30, 2015, and 2014, respectively, as their effect would have been antidilutive.

Estimated Fair Value of Financi

Estimated Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2015
Estimated Fair Value of Financial Instruments
Estimated Fair Value of Financial Instruments	11. Estimated Fair Value of Financial Instruments Authoritative guidance issued by FASB establishes a hierarchy of valuation techniques based on the observability of inputs utilized in measuring assets and liabilities at fair values. This hierarchy establishes market-based or observable inputs as the preferred source of values, followed by valuation models using management assumptions in the absence of market inputs. The three levels of the hierarchy under the authoritative guidance are as follows: Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the assessment date. Level 2 — Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 3 — Unobservable inputs for the asset or liability. Our financial instruments consist of cash and cash equivalents, accounts and other receivables, interest rate swaps, the revolving credit facility, the senior unsecured term loans, interest payable and accounts payable. The carrying values of cash and cash equivalents, accounts and other receivables, interest payable and accounts payable approximate fair values due to the short-term nature of these financial instruments. Interest rate swaps are carried at fair value. We have determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy; however, the credit valuation adjustments associated with our derivatives utilize Level 3 inputs, such as estimates of current credit spreads, to evaluate the likelihood of default by the Operating Partnership and its counterparties. As of June 30, 2015, we have assessed the significance of the impact of the credit valuation adjustments on the overall valuation of our derivative positions and has determined that the credit valuation adjustment is not significant to the overall valuation of our derivative portfolio. As a result, we classify our derivative valuation in Level 2 of the fair value hierarchy. The total balance of our revolving credit facility and senior unsecured term loans was $352.3 million as of June 30, 2015, with a fair value that approximated book value based on Level 3 inputs from the fair value hierarchy. Under the discounted cash flow method, the fair values of the revolving credit facility and the senior unsecured term loans are based on our assumptions of market interest rates and terms available incorporating our credit risk.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2015
Commitments and Contingencies
Commitments and Contingencies	12. Commitments and Contingencies Our properties require periodic investments of capital for general capital improvements and for tenant-related capital expenditures. We enter into various construction and equipment contracts with third parties for the development of our properties. In addition, we enter into contracts for company-wide improvements that are ancillary to revenue generation. At June 30, 2015, we had open commitments related to construction contracts of approximately $14.6 million. Additionally, we have commitments related to telecommunications capacity used to connect data centers located within the same market or geographical area and power usage. At June 30, 2015, we had open commitments related to these contracts of approximately $11.4 million. In April 2015, we executed a pre-lease and began construction of a 136,580 square-foot build-to-suit powered shell data center, which will be known as SV6, on land we own on our Santa Clara campus. We have incurred $5.0 million of the estimated $30.0 million required to complete the project, and expect to deliver the powered shell to a strategic customer in the first half of 2016. From time to time, we are party to a variety of legal proceedings arising in the ordinary course of business. We believe that, with respect to any such matter to which we currently are a party, the ultimate disposition of any such matter will not result in a material adverse effect on our business, financial condition, cash flows or results of operations.

Summary of Significant Accoun20

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2015
Summary of Significant Accounting Policies
Principles of Consolidation and Basis of Presentation	Principles of Consolidation and Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared by our management in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and in compliance with the rules and regulations of the United States Securities and Exchange Commission. Accordingly, these unaudited condensed consolidated financial statements do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of our management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. The results of operations for six months ended June 30, 2015, are not necessarily indicative of the expected results for the year ending December 31, 2015. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2014. Intercompany balances and transactions have been eliminated upon consolidation. In February 2015, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2015-02, Amendments to the Consolidation Analysis , which amends the current consolidation guidance. ASU 2015-02 is effective for annual and interim periods beginning after December 15, 2015, with early adoption permitted. The standard permits the use of either modified retrospective or cumulative effect transition method. We have not elected early adoption and we are currently evaluating the impact of the provisions of ASU 2015-02 on our consolidation policies as well as the transition method to be used to implement ASU 2015-02.
Use of Estimates	Use of Estimates The preparation of these unaudited condensed consolidated financial statements in conformity with GAAP requires our management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingencies at the date of the unaudited condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. We evaluate our estimates, including those related to assessing the carrying values of our real estate properties, goodwill, accrued liabilities and performance-based equity compensation plans. We base our estimates on historical experience, current market conditions, and various other assumptions that we believe to be reasonable under the circumstances. Actual results may vary from those estimates and those estimates could vary under different assumptions or conditions.
Adjustments and Reclassifications	Adjustments and Reclassifications Certain immaterial amounts included in the condensed consolidated financial statements for 2014 have been reclassified to conform to the 2015 financial statement presentation.
Investments in Real Estate	Investments in Real Estate Real estate investments are carried at cost less accumulated depreciation and amortization. The cost of real estate includes the purchase price of property and leasehold improvements. Expenditures for maintenance and repairs are expensed as incurred. Significant renovations and betterments that extend the economic useful lives of assets are capitalized. During land development and construction periods, we capitalize construction costs, legal fees, financing costs, real estate taxes and insurance and internal costs of personnel performing development, if such costs are incremental and identifiable to a specific development project. Capitalization of costs begins upon commencement of development efforts and ceases when the property is ready for its intended use and held available for occupancy. Interest is capitalized during the period of development based upon applying the weighted-average borrowing rate to the actual development costs expended. Capitalized interest costs were $1.0 million and $1.0 million for the three months ended June 30, 2015, and 2014, respectively, and $2.3 million and $2.2 million for the six months ended June 30, 2015, and 2014, respectively. Depreciation and amortization are calculated using the straight-line method over the following useful lives of the assets: Buildings 27 to 40 years Building improvements 1 to 10 years Leasehold improvements The shorter of the lease term or useful life of the asset Depreciation expense was $19.2 million and $15.9 million for the three months ended June 30, 2015, and 2014, respectively, and $37.1 million and $31.0 million for the six months ended June 30, 2015, and 2014, respectively.
Acquisition of Investment in Real Estate	Acquisition of Investment in Real Estate Purchase accounting is applied to the assets and liabilities related to all real estate investments acquired. The fair value of the real estate acquired is allocated to the acquired tangible assets, consisting primarily of land, building and building improvements, and identified intangible assets and liabilities, consisting of the value of above-market and below-market leases, value of in-place leases and the value of customer relationships. The fair value of the land and building of an acquired property is determined by valuing the property as if it were vacant, and the “as-if-vacant” fair value is then allocated to land and building based on management’s determination of the fair values of these assets. Management determines the as-if-vacant fair value of a property using methods similar to those used by independent appraisers. Factors considered by management in performing these analyses include an estimate of carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases. The fair value of intangibles related to in-place leases includes the value of lease intangibles for above-market and below-market leases, lease origination costs, and customer relationships, determined on a lease-by-lease basis. Above-market and below-market leases are valued based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) management’s estimate of fair market lease rates for the corresponding in-place leases, measured over a period equal to the remaining noncancelable term of the lease and, for below-market leases, over a period equal to the initial term plus any below-market fixed rate renewal periods. Lease origination costs include estimates of costs avoided associated with leasing the property, including tenant allowances and improvements and leasing commissions. Customer relationship intangibles relate to the additional revenue opportunities expected to be generated through interconnection services and utility services to be provided to the in-place lease tenants. The capitalized values for above and below-market lease intangibles, lease origination costs, and customer relationships are amortized over the term of the underlying leases or the expected customer relationship. Amortization related to above-market and below-market leases where the Company is the lessor is recorded as either a reduction of or an increase to rental income, amortization related to above-market and below-market leases where the Company is the lessee is recorded as either a reduction of or an increase to rent expense. If a lease is terminated prior to its stated expiration, all unamortized amounts relating to that lease are written off. The carrying value of intangible assets is reviewed for impairment in connection with its respective asset group whenever events or changes in circumstances indicate that the asset group may not be recoverable. An impairment loss is recognized if the carrying amount of the asset group is not recoverable and its carrying amount exceeds its estimated fair value. No impairment loss related to these intangible assets was recognized for either the three or six months ended June 30, 2015, or 2014. The excess of the cost of an acquired business over the net of the amounts assigned to assets acquired (including identified intangible assets) and liabilities assumed is recorded as goodwill. As of June 30, 2015, and December 31, 2014, we had approximately $41.2 million of goodwill at each date. The Company’s goodwill has an indeterminate life and is not amortized, but is tested for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the asset might be impaired. No impairment loss was recognized for either the three or six months ended June 30, 2015, or 2014.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include all non-restricted cash held in financial institutions and other non-restricted highly liquid short-term investments with original maturities at acquisition of three months or less.
Deferred Costs	Deferred Costs Deferred leasing costs include commissions paid to third parties, including leasing agents, and internal sales commissions paid to employees for successful execution of lease agreements. These commissions and other direct and incremental costs incurred to obtain new customer leases are capitalized and amortized over the terms of the related leases using the straight-line method. If a lease terminates prior to the expiration of its initial term, any unamortized deferred costs related to the lease are written off to amortization expense. Deferred leasing costs are included within other assets in the condensed consolidated balance sheets and consisted of the following, net of amortization, as of June 30, 2015, and December 31, 2014 (in thousands): June 30, December 31, 2015 2014 Internal sales commissions $ $ Third party commissions External legal counsel Total $ $ Deferred financing costs include costs incurred in connection with obtaining debt and extending existing debt. These financing costs are capitalized and amortized on a straight-line basis, which approximates the effective-interest method, over the term of the loan and the amortization is included as a component of interest expense. In March 2015, the FASB issued ASU 2015-03, Simplifying the Presentation of Debt Issuance Costs , which amends the current imputation of interest guidance. ASU 2015-03 is effective for annual and interim periods beginning after December 15, 2015, with early adoption permitted. We have not elected early adoption and we are currently evaluating the impact of the provisions of ASU 2015-03 on our balance sheet presentation.
Recoverability of Long-Lived Assets	Recoverability of Long-Lived Assets We review our long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Impairment is recognized when estimated expected future cash flows (undiscounted and without interest charges) are less than the carrying amount of the assets. The estimation of expected future net cash flows is inherently uncertain and relies, to a considerable extent, on assumptions regarding current and future economics and market conditions and the availability of capital. If, in future periods, there are changes in the estimates or assumptions incorporated into the impairment review analysis, the changes could result in an adjustment to the carrying amount of the long-lived assets. To the extent that impairment has occurred, the excess of the carrying amount of long-lived assets over its estimated fair value would be recognized as an impairment loss charged to net income. For the three and six months ended June 30, 2015, and 2014, no impairment of long-lived assets was recognized.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities We reflect all derivative instruments at fair value as either assets or liabilities on the condensed consolidated balance sheets. For those derivative instruments that are designated and qualify as hedging instruments, we record the effective portion of the gain or loss on the hedge instruments as a component of accumulated other comprehensive income or loss. Any ineffective portion of a derivative’s change in fair value is immediately recognized within net income. For derivatives that do not meet the criteria for hedge accounting, changes in fair value are immediately recognized within net income. See additional discussion in Note 6.
Internal-Use Software	Internal-Use Software We recognize internal-use software development costs based on the development stage of the project and nature of the cost. Internal and external costs incurred during the preliminary project stage are expensed as they are incurred. Internal and external costs incurred to develop internal-use software during the application development stage are capitalized. Internal and external training costs and maintenance costs during the post-implementation-operation stage are expensed as incurred. Completed projects are placed into service and amortized over the estimated useful life of the software. Impairment recognized, related to internal use software, in the condensed consolidated statements of operations during the three months ended June 30, 2015, and 2014, was zero and $1.0 million, respectively, and impairment recognized during the six months ended June 30, 2015, and 2014, was zero and $2.0 million, respectively. In April 2015, the FASB issued ASU 2015-05, Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement , which provides explicit guidance to help companies evaluate the accounting for fees paid by a customer in a cloud computing arrangement. ASU 2015-05 is effective for annual and interim beginning after December 15, 2015, with early adoption permitted. We have not elected early adoption and we are currently evaluating the impact of the provisions of ASU 2015-05 on our consolidated financial statements.
Revenue Recognition	Revenue Recognition All customer leases are classified as operating leases and minimum rents are recognized on a straight-line basis over the noncancelable term of the agreements. The excess of rents recognized over amounts contractually due pursuant to the underlying leases are included in deferred rent receivable. If a lease terminates prior to its stated expiration, the deferred rent receivable relating to that lease is written off as a reduction of rental revenue. When arrangements include multiple elements, the revenue associated with separate elements is allocated based on the relative fair values of those elements. The revenue associated with each element is then recognized as earned. Interconnection services and additional space services are considered as separate earnings processes that are provided and completed on a month-to-month basis and revenue is recognized in the period that services are performed. Customer set-up charges and utility installation fees are initially deferred and recognized over the term of the arrangement as revenue. Tenant reimbursements for real estate taxes, common area maintenance, and other recoverable costs are recognized as revenue in the period that the related expenses are incurred. Above-market and below-market lease intangibles that were acquired are amortized on a straight-line basis as decreases and increases, respectively, to rental revenue over the remaining noncancelable term of the underlying leases. For each of the three month periods ended June 30, 2015, and 2014, the net effect of amortization of acquired above-market and below-market leases resulted in an increase to rental revenue of $0.1 million. For the six months ended June 30, 2015, and 2014, the net effect of amortization of acquired above-market and below-market leases resulted in an increase to rental revenue of $0.3 million and $0.2 million, respectively. A provision for uncollectible accounts is recorded if a receivable balance relating to contractual rent, rent recorded on a straight-line basis, tenant reimbursements or other billed amounts is considered by management to be uncollectible. At June 30, 2015, and December 31, 2014, the allowance for doubtful accounts totaled $0.1 million and $0.1 million, respectively. In May 2014, the FASB issued guidance codified in Accounting Standards Codification (“ASC”) 606, Revenue Recognition — Revenue from Contracts with Customers , which amends the guidance in former ASC 605, Revenue Recognition . The standard is effective for interim and annual reporting periods beginning after December 15, 2016. The standard permits the use of either the retrospective or cumulative effect transition method. We are currently evaluating the impact of the provisions of ASC 606 on our revenue recognition policies as well as the transition method to be used to implement this guidance.
Share-Based Compensation	Share-Based Compensation We account for share-based compensation using the fair value method of accounting. The estimated fair value of the stock options granted by us is calculated based on the Black-Scholes option-pricing model. The fair value of restricted share-based and Operating Partnership unit compensation is based on the market value of our common stock on the date of the grant. The fair value of performance share awards, which have a market condition, is based on a Monte Carlo simulation. The fair value for all share-based compensation is amortized on a straight-line basis over the vesting period.
Asset Retirement and Environmental Remediation Obligations	Asset Retirement and Environmental Remediation Obligations We record accruals for estimated asset retirement and environmental remediation obligations. The obligations relate primarily to the removal of asbestos and contaminated soil during development of properties as well as the estimated equipment removal costs upon termination of a certain lease where we are the lessee. At both June 30, 2015, and December 31, 2014, the amount included in unearned revenue, prepaid rent and other liabilities on the condensed consolidated balance sheets was approximately $2.3 million.
Income Taxes	Income Taxes We elected to be taxed as a REIT under the Internal Revenue Code of 1986, as amended (the “Code”), commencing with our taxable year ended December 31, 2010. To qualify as a REIT, we are required to distribute at least 90% of our taxable income to our stockholders and meet various other requirements imposed by the Code relating to such matters as operating results, asset holdings, distribution levels and diversity of stock ownership. Provided we qualify for taxation as a REIT, we generally are not subject to corporate level federal income tax on the earnings distributed currently to our stockholders. If we fail to qualify as a REIT in any taxable year, and are unable to avail ourselves of certain savings provisions set forth in the Code, all of our taxable income would be subject to federal income tax at regular corporate rates, including any applicable alternative minimum tax. To maintain REIT status, we must distribute a minimum of 90% of our taxable income. However, it is our policy and intent, subject to change, to distribute 100% of our taxable income and therefore no provision is required in the accompanying condensed consolidated financial statements for federal income taxes with regards to activities of the REIT and its subsidiary pass-through entities. The allocable share of taxable income is included in the income tax returns of its stockholders. The Company is subject to the statutory requirements of the locations in which it conducts business. State and local income taxes are accrued as deemed required in the best judgment of management based on analysis and interpretation of respective tax laws. We have elected to treat certain subsidiaries as taxable REIT subsidiaries (“TRS”). Certain activities that we undertake must be conducted by a TRS, such as services for our tenants that could be considered otherwise impermissible for us to perform and holding assets that we cannot hold directly. A TRS is subject to corporate level federal and state income taxes. Deferred income taxes are recognized in certain taxable entities. Deferred income tax generally is a function of the period’s temporary differences (items that are treated differently for tax purposes than for financial reporting purposes), the utilization of tax net operating losses generated in prior years that previously had been recognized as deferred income tax assets and the reversal of any previously recorded deferred income tax liabilities. A valuation allowance for deferred income tax assets is provided if we believe all or some portion of the deferred income tax asset may more likely than not be not realized. Any increase or decrease in the valuation allowance resulting from a change in circumstances that causes a change in the estimated realizability of the related deferred income tax asset is included in deferred tax expense. As of June 30, 2015, and December 31, 2014, the gross deferred income taxes were not material. We currently have no liabilities for uncertain income tax positions. The earliest tax year for which we are subject to examination is 2011.
Concentration of Credit Risks	Concentration of Credit Risks Our cash and cash equivalents are maintained in various financial institutions, which, at times, may exceed federally insured limits. We have not experienced any losses in such accounts, and management believes that the Company is not exposed to any significant credit risk in this area. We have no off-balance sheet concentrations of credit risk, such as foreign exchange contracts, option contracts, or foreign currency hedging arrangements.
Segment Information	Segment Information We manage our business as one reportable segment consisting of investments in data centers located in the United States. Although we provide services in several markets, these operations have been aggregated into one reportable segment based on the similar economic characteristics amongst all markets, including the nature of the services provided and the type of customers purchasing these services.

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2015
Summary of Significant Accounting Policies
Schedule of useful lives of real estate investment assets	Buildings 27 to 40 years Building improvements 1 to 10 years Leasehold improvements The shorter of the lease term or useful life of the asset
Schedule of deferred leasing costs, net of amortization	Deferred leasing costs are included within other assets in the condensed consolidated balance sheets and consisted of the following, net of amortization, as of June 30, 2015, and December 31, 2014 (in thousands): June 30, December 31, 2015 2014 Internal sales commissions $ $ Third party commissions External legal counsel Total $ $

Investment in Real Estate (Tabl

Investment in Real Estate (Tables)	6 Months Ended
	Jun. 30, 2015
Investment in Real Estate
Summary of properties owned or leased	The following is a summary of the properties owned or leased at June 30, 2015 (in thousands): Buildings and Construction Property Name Location Land Improvements in Progress Total Cost SV1 San Jose, CA $ $ $ $ SV2 Milpitas, CA SV3 Santa Clara, CA SV4 Santa Clara, CA SV5 Santa Clara, CA — SV6 Santa Clara, CA — — Santa Clara Campus(1) Santa Clara, CA BO1 Somerville, MA NY1* New York, NY — NY2 Secaucus, NJ VA1 Reston, VA VA2 Reston, VA DC1* Washington, DC — CH1 Chicago, IL LA1* Los Angeles, CA — LA2 Los Angeles, CA MI1 Miami, FL DE1* Denver, CO — DE2* Denver, CO — — Total $ $ $ $ * Indicates properties in which we hold a leasehold interest. (1) This campus includes office and light-industrial buildings and land held for development in Santa Clara, California.

Other Assets (Tables)

Other Assets (Tables)	6 Months Ended
	Jun. 30, 2015
Other Assets
Schedule of other assets	Our other assets consisted of the following, net of amortization and depreciation, if applicable, as of June 30, 2015, and December 31, 2014 (in thousands): June 30, December 31, 2015 2014 Deferred leasing costs $ $ Deferred rent receivable Corporate furniture, fixtures and equipment Internal-use software Deferred financing costs Prepaid expenses Other Total $ $

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2015
Debt
Summary of outstanding indebtedness	A summary of outstanding indebtedness as of June 30, 2015, and December 31, 2014, is as follows (in thousands): Maturity June 30, December 31, Interest Rate Date 2015 2014 Revolving credit facility 1.73% and 2.17% at June 30, 2015, and December 31, 2014, respectively June 24, 2019 $ $ 2019 Senior unsecured term loan(1) 3.23% at June 30, 2015, and at December 31, 2014 January 31, 2019 2020 Senior unsecured term loan(2) 2.31% at June 30, 2015 June 24, 2020 — Total principal outstanding $ $ (1) The Operating Partnership elected to swap the variable interest rate associated with the 2019 Senior unsecured term loan to a fixed rate of approximately 3.23% per annum at our current leverage ratio. (2) The Operating Partnership elected to swap the variable interest rate associated with $75 million, or 50%, of the principal amount of the 2020 Senior unsecured term loan to a fixed rate of approximately 2.93% per annum at our current leverage ratio. The interest rate on the remaining $75 million of the 2020 Senior unsecured term loan is based on LIBOR plus the applicable spread. The effective interest rate as of June 30, 2015, is 2.31%.
Summary of amount of the entity's outstanding debt when such debt currently become due	The following table summarizes the amount of our outstanding debt as of June 30, 2015 , when such debt currently becomes due (in thousands) : Year Ending December 31, Remainder of 2015 $ — 2016 — 2017 — 2018 — 2019 2020 Total $

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2015
Stockholders' Equity
Schedule of dividends paid per share on Series A Cumulative Preferred Stock and common shares	We paid the following dividends per share on our Series A cumulative preferred stock and common stock during the six months ended June 30, 2015: Declaration Date Record Date Payment Date Preferred Stock Common Stock March 12, 2015 March 31, 2015 April 15, 2015 $ (1) $ May 21, 2015 June 30, 2015 July 15, 2015 (2) $ $ (1) Dividend covers the period from January 15, 2015, to April 14, 2015. (2) Dividend covers the period from April 15, 2015, to July 14, 2015.

Noncontrolling Interests - Op26

Noncontrolling Interests - Operating Partnership (Tables)	6 Months Ended
	Jun. 30, 2015
Noncontrolling Interests - Operating Partnership
Schedule of ownership interests in the Operating Partnership	June 30, 2015 December 31, 2014 Number of Units Percentage of Total Number of Units Percentage of Total CoreSite Realty Corporation % % Noncontrolling interests % % Total % %

Equity Incentive Plan (Tables)

Equity Incentive Plan (Tables)	6 Months Ended
	Jun. 30, 2015
Equity Incentive Plan
Schedule of stock option activity	Number of Shares Subject to Options Weighted- Average Exercise Price Options outstanding, December 31, 2014 $ Granted — — Exercised ) Forfeited ) Expired ) Options outstanding, June 30, 2015 $
Schedule of unvested shares subject to options	Number of Shares Subject to Options Weighted- Average Fair Value at Grant Date Unvested balance, December 31, 2014 $ Granted — — Forfeited ) Vested ) Unvested balance, June 30, 2015 $
Schedule of restricted awards and RSUs	Restricted Awards Weighted- Average Fair Value at Grant Date Unvested balance, December 31, 2014 $ Granted Forfeited ) Vested ) Unvested balance, June 30, 2015 $
Summary of assumptions used to value performance stock awards	Six Months Ended June 30, 2015 2014 Expected term (in years) Expected volatility % % Expected annual dividend — — Risk-free rate % %

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2015
Earnings Per Share
Summary of basic and diluted income per share	Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Net income attributable to common shares $ $ $ $ Weighted-average common shares outstanding - basic Effect of potentially dilutive common shares: Stock options Unvested awards Weighted-average common shares outstanding - diluted Net income per share attributable to common shares Basic $ $ $ $ Diluted $ $ $ $

Organization and Description 29

Organization and Description of Business (Details) - Common Stock - Operating partnership	Jun. 30, 2015
Organization
Percentage of ownership interests held by the entity	55.50%
Percentage of ownership interests held by others	44.50%

Summary of Significant Accoun30

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investments in Real Estate
Capitalized interest costs	$ 1	$ 1	$ 2.3	$ 2.2
Depreciation expense	$ 19.2	$ 15.9	$ 37.1	$ 31
Building | Minimum
Investments in Real Estate
Useful lives	27 years
Building | Maximum
Investments in Real Estate
Useful lives	40 years
Building Improvements | Minimum
Investments in Real Estate
Useful lives	1 year
Building Improvements | Maximum
Investments in Real Estate
Useful lives	10 years

Summary of Significant Accoun31

Summary of Significant Accounting Policies (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Deferred Costs
Internal sales commissions	$ 15,598		$ 15,598		$ 13,171
Third party commissions	12,594		12,594		13,665
External legal counsel	567		567		393
Total	28,759		28,759		27,229
Recoverability of Long-Lived Assets
Impairment of real estate	0	$ 0	0	$ 0
Impairment loss related to intangible assets	0	0	0	0
Goodwill	41,191		41,191		$ 41,191
Impairment loss related to goodwill	$ 0	$ 0	$ 0	$ 0

Summary of Significant Accoun32

Summary of Significant Accounting Policies (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Internal-Use Software
Capitalized Computer Software Impairment		$ 1,037		$ 1,959
Revenue Recognition
Increase to rental revenue	$ 100	$ 100	$ 300	$ 200
Allowance for doubtful accounts (in dollars)	132		132		$ 112
Asset Retirement and Environmental Remediation Obligations
Asset retirement and environmental remediation obligations	2,300		$ 2,300		$ 2,300
Income taxes
Minimum percentage of distribution of taxable income to qualify as REIT			90.00%
Percentage of distribution of taxable income as per company policy			100.00%
Provision for federal income taxes			$ 0
Liabilities for uncertain positions	$ 0		$ 0

Summary of Significant Accoun33

Summary of Significant Accounting Policies (Details 4)	6 Months Ended
	Jun. 30, 2015item
Summary of Significant Accounting Policies
Number of off-balance-sheet concentrations of credit risk	0
Segment information
Number of reportable segments	1

Investment in Real Estate (Deta

Investment in Real Estate (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Investment in Real Estate
Land	$ 78,337	$ 78,983
Buildings and Improvements	1,012,845	888,966
Construction in progress	106,872	$ 178,599
Total investments in real estate	1,198,054
SV1 San Jose CA
Investment in Real Estate
Land	6,863
Buildings and Improvements	127,032
Construction in progress	469
Total investments in real estate	134,364
SV2 Milpitas CA
Investment in Real Estate
Land	5,086
Buildings and Improvements	26,822
Construction in progress	680
Total investments in real estate	32,588
SV3 Santa Clara CA
Investment in Real Estate
Land	3,972
Buildings and Improvements	49,146
Construction in progress	295
Total investments in real estate	53,413
SV4 Santa Clara CA
Investment in Real Estate
Land	4,501
Buildings and Improvements	90,806
Construction in progress	726
Total investments in real estate	96,033
SV5 Santa Clara CA
Investment in Real Estate
Land	2,544
Buildings and Improvements	23,514
Total investments in real estate	26,058
SV6 Santa Clara CA
Investment in Real Estate
Construction in progress	17,142
Total investments in real estate	17,142
Santa Clara Campus Properties Santa Clara CA
Investment in Real Estate
Land	3,518
Buildings and Improvements	2,916
Construction in progress	4,239
Total investments in real estate	10,673
BO1 Somerville MA
Investment in Real Estate
Land	5,154
Buildings and Improvements	81,982
Construction in progress	265
Total investments in real estate	87,401
NY1 New York NY
Investment in Real Estate
Buildings and Improvements	34,369
Construction in progress	8
Total investments in real estate	34,377
NY2 Secaucus NJ
Investment in Real Estate
Land	2,388
Buildings and Improvements	89,075
Construction in progress	36,719
Total investments in real estate	128,182
VA1 Reston VA
Investment in Real Estate
Land	6,903
Buildings and Improvements	114,724
Construction in progress	4,131
Total investments in real estate	125,758
VA2 Reston VA
Investment in Real Estate
Land	2,720
Buildings and Improvements	63,177
Construction in progress	32,105
Total investments in real estate	98,002
DC1 Washington DC
Investment in Real Estate
Buildings and Improvements	7,976
Construction in progress	151
Total investments in real estate	8,127
CH1 Chicago IL
Investment in Real Estate
Land	5,493
Buildings and Improvements	87,109
Construction in progress	5,363
Total investments in real estate	97,965
LA1 Los Angeles CA
Investment in Real Estate
Buildings and Improvements	63,340
Construction in progress	2,514
Total investments in real estate	65,854
LA2 Los Angeles CA
Investment in Real Estate
Land	28,467
Buildings and Improvements	136,684
Construction in progress	1,831
Total investments in real estate	166,982
MI1 Miami FL
Investment in Real Estate
Land	728
Buildings and Improvements	10,332
Construction in progress	2
Total investments in real estate	11,062
DE1 Denver CO
Investment in Real Estate
Buildings and Improvements	2,789
Construction in progress	232
Total investments in real estate	3,021
DE2 Denver CO
Investment in Real Estate
Buildings and Improvements	1,052
Total investments in real estate	$ 1,052

Other Assets (Details)

Other Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Other Assets
Deferred leasing costs	$ 28,759	$ 27,229
Deferred rent receivable	24,425	21,510
Corporate furniture, fixtures and equipment	7,752	7,980
Internal-use software	4,141	2,421
Deferred financing costs	7,100	7,474
Prepaid expense	4,288	6,251
Other	1,104	2,735
Total	77,569	75,600
Estimated amortization of deferred leasing costs
Total	$ 28,759	$ 27,229

Debt (Details)

Debt (Details) $ in Thousands	Jun. 24, 2015USD ($)	Jan. 31, 2014USD ($)	Jun. 30, 2015USD ($)item	Dec. 31, 2014USD ($)
Debt
Total principal outstanding			$ 352,250	$ 318,500
Credit Agreement | Operating partnership
Debt
Commitment under the credit agreement	$ 500,000		$ 500,000
Number of options available for extensions | item			1
Extension fee (as a percent)			0.10%
Revolving Credit Facility
Debt
Interest rate as of reporting date (as a percent)			1.73%	2.17%
Total principal outstanding			$ 102,250	$ 218,500
Letters of credit outstanding			6,300
Amount available for borrowing under the facility			$ 241,400
Leverage ratio (as a percent)			17.90%
Secured debt ratio (as a percent)			0.00%
Fixed charge coverage ratio			8.4
Unhedged variable rate debt ratio (as a percent)			8.30%
Revolving Credit Facility | Operating partnership
Debt
Commitment under the credit agreement	350,000
Iincreased commitment under accordion feature			$ 700,000
Revolving Credit Facility | Minimum
Debt
Fixed charge coverage ratio, Covenant			1.70
Revolving Credit Facility | Maximum
Debt
Leverage ratio (as a percent)			0.60%
Secured debt ratio, Covenant (as a percent)			0.40%
Unhedged variable rate debt ratio (as a percent)			0.30%
Revolving Credit Facility | LIBOR | Operating partnership
Debt
Reference rate			LIBOR
Interest rate margin (as a percent)			1.55%
Leverage ratio (as a percent)			17.90%
Revolving Credit Facility | LIBOR | Minimum | Operating partnership
Debt
Interest rate margin (as a percent)			1.55%
Revolving Credit Facility | LIBOR | Maximum | Operating partnership
Debt
Interest rate margin (as a percent)			2.25%
Revolving Credit Facility | Base rate | Operating partnership
Debt
Reference rate			base rate
Revolving Credit Facility | Base rate | Minimum | Operating partnership
Debt
Interest rate margin (as a percent)			0.55%
Revolving Credit Facility | Base rate | Maximum | Operating partnership
Debt
Interest rate margin (as a percent)			1.25%
Revolving Credit Facility Prior Facility
Debt
Commitment under the credit agreement	405,000
2020 Senior Unsecured Term Loan
Debt
Interest rate as of reporting date (as a percent)			2.31%
Total principal outstanding			$ 150,000
Percentage of debt hedged			50.00%
Interest rate margin (as a percent)			2.93%
Amount available for borrowing under the facility			$ 75,000
2020 Senior Unsecured Term Loan | Operating partnership
Debt
Total principal outstanding	150,000
Unsecured term loan	$ 150,000
Term of loan facility	5 years
Leverage ratio (as a percent)			17.90%
2020 Senior Unsecured Term Loan | LIBOR | Operating partnership
Debt
Interest rate margin (as a percent)			1.50%
2020 Senior Unsecured Term Loan | LIBOR | Minimum | Operating partnership
Debt
Interest rate margin (as a percent)			1.50%
2020 Senior Unsecured Term Loan | LIBOR | Maximum | Operating partnership
Debt
Interest rate margin (as a percent)			2.20%
2020 Senior Unsecured Term Loan | Base rate | Minimum | Operating partnership
Debt
Interest rate margin (as a percent)			0.50%
2020 Senior Unsecured Term Loan | Base rate | Maximum | Operating partnership
Debt
Interest rate margin (as a percent)			1.20%
2019 Senior Unsecured Term Loan
Debt
Interest rate as of reporting date (as a percent)			3.23%	3.23%
Total principal outstanding			$ 100,000	$ 100,000
2019 Senior Unsecured Term Loan | Operating partnership
Debt
Commitment under the credit agreement		$ 100,000
Term of loan facility		5 years
Total increase in commitment under accordion feature		$ 100,000
Iincreased commitment under accordion feature		$ 200,000
2019 Senior Unsecured Term Loan | LIBOR | Operating partnership
Debt
Reference rate		LIBOR	LIBOR
Interest rate margin (as a percent)			1.75%
Leverage ratio (as a percent)			17.90%
2019 Senior Unsecured Term Loan | LIBOR | Minimum | Operating partnership
Debt
Interest rate margin (as a percent)		1.75%
2019 Senior Unsecured Term Loan | LIBOR | Maximum | Operating partnership
Debt
Interest rate margin (as a percent)		2.65%
2019 Senior Unsecured Term Loan | Base rate | Operating partnership
Debt
Reference rate		base rate
2019 Senior Unsecured Term Loan | Base rate | Minimum | Operating partnership
Debt
Interest rate margin (as a percent)		0.75%
2019 Senior Unsecured Term Loan | Base rate | Maximum | Operating partnership
Debt
Interest rate margin (as a percent)		1.65%

Debt (Details 2)

Debt (Details 2) $ in Thousands	Jun. 30, 2015USD ($)
Debt maturities
2,019	$ 202,250
2,020	150,000
Total	$ 352,250

Derivatives and Hedging Activ38

Derivatives and Hedging Activities (Details) - USD ($)	Apr. 09, 2015	Feb. 03, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Derivative instruments and hedging activities disclosures
Amount of gain (loss) recorded in accumulated other comprehensive income			$ 448,000	$ (1,271,000)	$ (861,000)	$ (754,000)
Interest Rate Swap | Designated as Hedging Instrument
Derivative instruments and hedging activities disclosures
Interest rate as of reporting date (as a percent)		3.23%
Amount borrowed under term loan or revolving credit facility		$ 100,000,000
Debt Instrument, Term		5 years
Interest Rate Swap | Designated as Hedging Instrument | Cash Flow Hedging
Derivative instruments and hedging activities disclosures
Interest rate as of reporting date (as a percent)	2.93%
Amount borrowed under term loan or revolving credit facility	$ 75,000,000
Debt Instrument, Term	5 years
Amount of gain (loss) recorded in accumulated other comprehensive income			400,000	(1,300,000)	(900,000)	(800,000)
Amount reclassified to interest expense			500,000	$ 300,000	800,000	$ 500,000
Amount estimated to be reclassified as an increase to interest expense			1,900,000
Amount recognized in prepaid rent and other liabilities			800,000		800,000		$ 300,000
Amount recognized in other assets relating to outstanding derivatives			$ 500,000		$ 500,000
Interest Rate Swap | LIBOR | Designated as Hedging Instrument
Derivative instruments and hedging activities disclosures
Reference rate	one-month LIBOR

Stockholders' Equity (Details)

Stockholders' Equity (Details) - $ / shares	Jun. 30, 2015	Mar. 31, 2015
Stockholders' Equity
Dividend declared (in dollars per share)	$ 0.9062	$ 0.84
Series A Cumulative Redeemable Preferred Stock
Stockholders' Equity
Dividend declared (in dollars per share)	0.4531	0.4531
Common Stock
Stockholders' Equity
Dividend declared (in dollars per share)	$ 0.42	$ 0.42

Noncontrolling Interests - Op40

Noncontrolling Interests - Operating Partnership (Details) $ / shares in Units, $ in Millions	Dec. 12, 2012shares	Jun. 30, 2015USD ($)$ / sharesshares	Dec. 31, 2014shares	May. 01, 2015USD ($)shares
Noncontrolling Interests Operating Partnership
Conversion ratio for common operating partnership units		1
Number of Units (in shares)		46,851,708	46,648,038
Common Stock, shares issued		26,531,414	21,757,366
Percentage of Total		100.00%	100.00%
Shares of common stock issued related to employee compensation arrangements		203,670
Quarterly distributions will receive by holders of operating partnership units (in dollars per unit) | $ / shares		$ 0.42
Preferred Stock, Dividend Rate, Percentage		7.25%	7.25%
CoreSite Realty Corporation
Noncontrolling Interests Operating Partnership
Number of Units (in shares)		25,990,861	21,287,191
Percentage of Total		55.50%	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)		20,860,847	25,360,847
Percentage of Total		44.50%	54.40%
Redemption value of the noncontrolling interests | $		$ 947.9		$ 59.1
Closing price of the Company's stock (in dollars per share) | $ / shares		$ 45.44
Noncontrolling Interest Common Units Held by Third Parties
Noncontrolling Interests Operating Partnership
Number of Units (in shares)				4,500,000
Common Stock, shares issued				4,500,000

Equity Incentive Plan (Details)

Equity Incentive Plan (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 03, 2015	Mar. 04, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	May. 22, 2013
Assumptions used to value the stock options granted
Expected term			2 years 9 months 29 days	2 years 9 months 29 days
Expected volatility (as a percent)			25.51%	32.98%
Risk-free rate (as a percent)			1.02%	0.64%
2010 Plan
Equity Incentive Plan
Shares of common stock that were available for issuance pursuant to the 2010 Plan			3,341,238		3,341,238		6,000,000
Stock Options
Number of Shares Subject to Options
Options outstanding at the beginning of the period (in shares)					758,095
Exercised (in shares)					(87,896)
Forfeited (in shares)					(3,968)
Expired (in shares)					(282)
Options outstanding at the end of the period (in shares)			665,949		665,949
Weighted Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)					$ 20.94
Exercised (in dollars per share)					17.41
Forfeited (in dollars per share)					25.94
Expired (in dollars per share)					15.23
Options outstanding at the end of the period (in dollars per share)			$ 21.38		$ 21.38
Number of Shares Subject to Options
Unvested balance at the beginning of the period (in shares)					283,964
Forfeited (in shares)					(3,968)
Vested (in shares)					(163,392)
Unvested balance at the end of the period (in shares)			116,604		116,604
Weighted Average Fair Value at Grant
Unvested balance at the beginning of the period (in dollars per share)					$ 7.75
Forfeited (in dollars per share)					8.05
Vested (in dollars per share)					6.82
Unvested balance at the end of the period (in dollars per share)			$ 9.03		$ 9.03
Compensation cost not yet recognized
Unearned compensation			$ 0.8		$ 0.8
Stock Options | Weighted Average
Compensation cost not yet recognized
Vesting period					1 year 4 months 24 days
Restricted Awards
Restricted Awards
Unvested balance at the beginning of the period (in shares)					394,016
Granted (in shares)					183,710
Forfeited (in shares)					(22,145)
Vested (in shares)					(158,815)
Unvested balance at the end of the period (in shares)			396,766		396,766
Weighted Average Fair Value at Grant
Unvested balance at the beginning of the period (in dollars per share)					$ 29.10
Granted (in dollars per share)					47.39
Forfeited (in dollars per share)					34.54
Vested (in dollars per share)					26.76
Unvested balance at the end of the period (in dollars per share)			$ 38.20		$ 38.20
Compensation cost not yet recognized
Unearned compensation			$ 13.3		$ 13.3
Restricted Awards | Weighted Average
Compensation cost not yet recognized
Vesting period					2 years 8 months 12 days
Restricted stock
Restricted Awards
Grant date value					$ 8.4
Granted (in shares)					176,582
RSUs
Restricted Awards
Granted (in shares)					7,128
PSAs
Restricted Awards
Grant date value	$ 2.7	$ 1.6
Granted (in shares)	78,553	91,335
Forfeited (in shares)					(3,637)	(3,782)
Compensation cost not yet recognized
Unearned compensation			$ 3.1		$ 3.1
Percentage of awards eligible to be earned upon TSR achievement in year one of the performance period					20.00%
Percentage of awards eligible to be earned upon TSR achievement in year two of the performance period					20.00%
Percentage of awards earned upon TSR achievement in year three of the performance period					20.00%
Percentage of awards eligible to be earned upon cumulative TSR achievement over the three-year performance period					40.00%
Number of awards failed to satisfy performance condition						6,872
PSAs | Weighted Average
Compensation cost not yet recognized
Vesting period					2 years 6 months
PSAs | Minimum
Compensation cost not yet recognized
Percentage of number of shares to be earned under awards	25.00%	0.00%
PSAs | Maximum
Compensation cost not yet recognized
Percentage of number of shares to be earned under awards	175.00%	150.00%

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share
Net income attributable to common shares	$ 5,538	$ 3,883	$ 10,106	$ 6,616
Weighted-average common shares outstanding - basic	24,536,583	21,131,077	22,963,111	21,062,299
Effect of potentially dilutive common shares:
Stock options	363,760	371,536	373,438	368,516
Unvested awards	154,852	102,117	188,767	168,934
Weighted-average common shares outstanding - diluted	25,055,195	21,604,730	23,525,316	21,599,749
Net income per share attributable to common shares
Basic (in dollars per share)	$ 0.23	$ 0.18	$ 0.44	$ 0.31
Diluted (in dollars per share)	$ 0.22	$ 0.18	$ 0.43	$ 0.31
Weighted-average potentially dilutive securities excluded in calculation of basic and diluted income (loss) per share	43,013	165,552	141,081	202,422

Estimated Fair Value of Finan43

Estimated Fair Value of Financial Instruments (Details) $ in Millions	Jun. 30, 2015USD ($)
Significant Unobservable Inputs (Level 3)
Fair value of assets and liabilities measured on a recurring basis
Balance of revolving credit facility and senior unsecured term loan	$ 352.3

Commitments and Contingencies (

Commitments and Contingencies (Details ) $ in Millions	1 Months Ended
	Apr. 30, 2015USD ($)ft²	Jun. 30, 2015USD ($)
Commitments and Contingencies
Development Costs, Cumulative	$ 30
Capital Expenditures Incurred but Not yet Paid	$ 5
Area of Land | ft²	136,580
Other expenses
Open commitments related to construction contracts		$ 14.6
Open commitments related to telecommunications contracts		$ 11.4