CoreSite Realty 10-K 14 Feb 14 2013 Q4 Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Feb. 12, 2014	Jun. 28, 2013
Document and Entity Information	'	'	'
Entity Registrant Name	'CoreSite Realty Corp	'	'
Entity Central Index Key	'0001490892	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
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 Public Float	'	'	$483
Entity Common Stock, Shares Outstanding	'	21,329,013	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'Q4	'	'

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Investments in real estate:	'	'
Land	$78,983	$85,868
Building and building improvements	717,007	596,405
Leasehold improvements	95,218	85,907
Total investments in real estate	891,208	768,180
Less: Accumulated depreciation and amortization	-155,704	-105,433
Net investment in operating properties	735,504	662,747
Construction in progress	157,317	61,328
Net investments in real estate	892,821	724,075
Cash and cash equivalents	5,313	8,130
Accounts and other receivables, net of allowance for doubtful accounts of $159 and $625 as of December 31, 2013, and 2012, respectively	10,339	9,901
Lease intangibles, net of accumulated amortization of $17,646 and $33,050 as of December 31, 2013, and 2012, respectively	11,028	19,453
Goodwill	41,191	41,191
Other assets	55,802	42,582
Total assets	1,016,494	845,332
Liabilities:	'	'
Revolving credit facility	174,250	'
Mortgage loan payable	58,250	59,750
Accounts payable and accrued expenses	67,782	50,624
Deferred rent payable	9,646	4,329
Acquired below-market lease contracts, net of accumulated amortization of $4,361 and $10,062 as of December 31, 2013, and 2012, respectively	6,681	8,539
Prepaid rent and other liabilities	11,578	11,317
Total liabilities	328,187	134,559
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 December 31, 2013, and 2012	115,000	115,000
Common Stock, par value $0.01, 100,000,000 shares authorized and 21,387,152 and 21,202,673 shares issued and outstanding at December 31, 2013, and 2012, respectively	209	207
Additional paid-in capital	267,465	259,009
Distributions in excess of net income	-50,264	-35,987
Total stockholders' equity	332,410	338,229
Noncontrolling interests	355,897	372,544
Total equity	688,307	710,773
Total liabilities and equity	$1,016,494	$845,332

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
CONSOLIDATED BALANCE SHEETS	'	'
Allowance for doubtful accounts (in dollars)	$159	$625
Accumulated amortization, lease intangibles (in dollars)	17,646	33,050
Accumulated amortization, acquired below-market lease contracts (in dollars)	4,361	10,062
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	21,387,152	21,202,673
Common Stock, shares outstanding	21,387,152	21,202,673

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Data center revenue:	'	'	'
Rental revenue	$131,080	$116,146	$101,449
Power revenue	59,663	53,672	43,661
Interconnection revenue	28,932	21,637	12,677
Tenant reimbursement and other	7,317	7,088	6,610
Office, light industrial and other revenue	7,841	8,391	8,449
Total operating revenues	234,833	206,934	172,846
Operating expenses:	'	'	'
Property operating and maintenance	64,260	61,235	55,049
Real estate taxes and insurance	8,458	8,765	9,119
Depreciation and amortization	65,785	64,327	68,967
Sales and marketing	14,405	10,330	5,744
General and administrative	27,317	25,910	21,846
Rent	19,659	18,711	18,336
Transaction costs	279	613	875
Total operating expenses	200,163	189,891	179,936
Operating income (loss)	34,670	17,043	-7,090
Gain on early extinguishment of debt	'	'	939
Interest income	32	13	117
Interest expense	-2,689	-5,236	-5,275
Income (loss) before income taxes	32,013	11,820	-11,309
Income tax (expense) benefit	-401	-1,104	530
Net income (loss)	31,612	10,716	-10,779
Net income (loss) attributable to noncontrolling interests	12,771	5,668	-6,168
Net income (loss) attributable to CoreSite Realty Corporation	18,841	5,048	-4,611
Preferred stock dividends	-8,338	-440	'
Net income(loss) attributable to common shares	$10,503	$4,608	($4,611)
Net income (loss) per share attributable to common shares:	'	'	'
Basic (in dollars per share)	$0.50	$0.22	($0.24)
Diluted (in dollars per share)	$0.49	$0.22	($0.24)
Weighted average common shares outstanding	'	'	'
Basic (in shares)	20,826,622	20,537,946	19,609,375
Diluted (in shares)	21,503,212	20,992,290	19,609,375

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)	'	'	'
Net income (loss)	$31,612	$10,716	($10,779)
Other comprehensive income (loss):	'	'	'
Unrealized gain (loss) on derivative contracts	'	-72	-366
Reclassification of other comprehensive income to interest expense	'	145	173
Comprehensive income (loss)	31,612	10,789	-10,972
Comprehensive income (loss) attributable to noncontrolling interests	17,323	5,951	-6,275
Comprehensive income (loss) attributable to common shares	$14,289	$4,838	($4,697)

CONSOLIDATED_STATEMENTS_OF_EQU

CONSOLIDATED STATEMENTS OF EQUITY (USD $)	Total	Total Stockholders' Equity	Preferred Stock	Common Shares	Additional Paid-in Capital	Distributions in Excess of Net Income	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
In Thousands, except Share data, unless otherwise specified
Balance at Dec. 31, 2010	$654,465	$232,239	'	$194	$239,453	($7,460)	$52	$422,226
Balance (in shares) at Dec. 31, 2010	'	'	'	19,644,042	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'
Redemption of noncontrolling interests	'	13,768	'	9	13,759	'	'	-13,768
Redemption of noncontrolling interests (in shares)	'	'	'	889,610	'	'	'	'
Issuance of restricted stock awards, net of forfeitures (in shares)	'	'	'	212,180	'	'	'	'
Exercise of stock options	31	31	'	'	31	'	'	'
Exercise of stock options (in shares)	'	'	'	1,962	'	'	'	'
Offering costs	-17	-17	'	'	-17	'	'	'
Amortization of deferred compensation	2,958	2,958	'	1	2,957	'	'	'
Dividends and distributions	-26,278	-11,474	'	'	'	-11,474	'	-14,804
Net income (loss)	-10,779	-4,611	'	'	'	-4,611	'	-6,168
Change in fair value on derivative contracts	-366	-163	'	'	'	'	-163	-203
Reclassification of other comprehensive income to interest expense	173	77	'	'	'	'	77	96
Balance at Dec. 31, 2011	620,187	232,808	'	204	256,183	-23,545	-34	387,379
Balance (in shares) at Dec. 31, 2011	'	'	'	20,747,794	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'
Issuance of restricted stock awards, net of forfeitures (in shares)	'	'	'	357,009	'	'	'	'
Exercise of stock options	1,564	1,564	'	1	1,563	'	'	'
Exercise of stock options (in shares)	'	'	'	97,870	'	'	'	'
Issuance of Series A Preferred Stock	110,615	110,615	115,000	'	-4,385	'	'	'
Amortization of deferred compensation	5,650	5,650	'	2	5,648	'	'	'
Dividends accumulated on preferred stock	-440	-440	'	'	'	-440	'	'
Dividends and distributions	-37,592	-17,050	'	'	'	-17,050	'	-20,542
Net income (loss)	10,716	5,048	'	'	'	5,048	'	5,668
Change in fair value on derivative contracts	-72	-31	'	'	'	'	-31	-41
Reclassification of other comprehensive income to interest expense	145	65	'	'	'	'	65	80
Balance at Dec. 31, 2012	710,773	338,229	115,000	207	259,009	-35,987	'	372,544
Balance (in shares) at Dec. 31, 2012	'	'	'	21,202,673	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'
Issuance of restricted stock awards, net of forfeitures	1	1	'	1	'	'	'	'
Issuance of restricted stock awards, net of forfeitures (in shares)	'	'	'	129,698	'	'	'	'
Exercise of stock options	925	925	'	1	924	'	'	'
Exercise of stock options (in shares)	'	'	'	54,781	'	'	'	'
Offering costs	-27	-27	'	'	-27	'	'	'
Amortization of deferred compensation	7,559	7,559	'	'	7,559	'	'	'
Dividends declared on preferred stock	-8,338	-8,338	'	'	'	-8,338	'	'
Dividends and distributions	-54,198	-24,780	'	'	'	-24,780	'	-29,418
Net income (loss)	31,612	18,841	'	'	'	18,841	'	12,771
Balance at Dec. 31, 2013	$688,307	$332,410	$115,000	$209	$267,465	($50,264)	'	$355,897
Balance (in shares) at Dec. 31, 2013	'	'	'	21,387,152	'	'	'	'

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES	'	'	'
Net income (loss)	$31,612	$10,716	($10,779)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:	'	'	'
Depreciation and amortization	65,785	64,327	68,967
Amortization of above/below market leases	-823	-1,505	-1,650
Amortization of deferred financing costs	1,739	1,681	1,556
Gain on early extinguishment of debt	'	'	-939
Share-based compensation	6,770	5,650	2,958
Amortization of discount to fair market value of acquired loan	'	'	687
Bad debt expense	244	544	292
Changes in operating assets and liabilities:	'	'	'
Accounts receivable	-682	-3,657	-1,523
Due to and due from related parties	'	'	2
Deferred rent receivable	-2,248	-3,966	-4,986
Deferred leasing costs	-6,852	-4,105	-4,215
Other assets	-7,157	-2,465	-515
Accounts payable and accrued expenses	3,756	2,245	7,273
Prepaid rent and other liabilities	262	-1,611	2,820
Deferred rent payable	5,317	794	1,258
Net cash provided by operating activities	97,723	68,648	61,206
CASH FLOWS FROM INVESTING ACTIVITIES	'	'	'
Tenant improvements	-7,128	-6,075	-5,328
Real estate improvements	-185,452	-83,837	-112,196
Acquisition of NY2	-21,889	'	'
Acquisition of Comfluent, net of cash received	'	-2,581	'
Changes in reserves for capital improvements	'	8,691	4,965
Net cash used in investing activities	-214,469	-83,802	-112,559
CASH FLOWS FROM FINANCING ACTIVITIES	'	'	'
Offering costs	'	'	-17
Proceeds from exercise of stock options	925	1,564	31
Gross proceeds from the issuance of Series A Preferred Stock	'	115,000	'
Series A Preferred Stock offering costs paid	-27	-4,190	'
Proceeds from revolving credit facility	174,250	72,750	5,000
Payments on revolving credit facility	'	-77,750	'
Proceeds from mortgage loans payable	'	'	6,440
Repayments of mortgage loans payable	-1,500	-57,114	-14,189
Payments of loan fees and costs	-2,621	-503	-1,745
Dividends and distributions	-57,098	-33,101	-23,785
Net cash provided by (used in) financing activities	113,929	16,656	-28,265
Net change in cash and cash equivalents	-2,817	1,502	-79,618
Cash and cash equivalents, beginning of period	8,130	6,628	86,246
Cash and cash equivalents, end of period	5,313	8,130	6,628
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION	'	'	'
Cash paid for interest	5,365	5,492	4,360
NON-CASH INVESTING AND FINANCING ACTIVITY	'	'	'
Construction costs payable capitalized to real estate	19,821	10,520	5,564
Accrual of dividends and distributions	$18,804	$13,384	$8,453

Organization

Organization	12 Months Ended
	Dec. 31, 2013
Organization	'
Organization	'
	1. Organization
	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 managing technology-related real estate or more commonly referred to as data centers. As of December 31, 2013, the Company owns a 45.2% common interest in the Operating Partnership.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
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 consolidated financial statements have been prepared by management in accordance with U.S. generally accepted accounting principles ("GAAP"). Intercompany balances and transactions have been eliminated in these consolidated financial statements. The Company reviewed subsequent events through the issuance date for inclusion in these consolidated financial statements.
	Use of Estimates
	The preparation of 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 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
	Office, light industrial and other revenue, included within the consolidated statements of operations for the years ended December 31, 2012, and 2011, have been reclassified to conform to the 2013 financial statement presentation. In addition, certain other immaterial amounts included in the consolidated financial statements for 2012 and 2011 have been reclassified to conform to the 2013 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 the 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 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 $4.4 million, $1.8 million and $1.6 million for the years ended December 31, 2013, 2012, and 2011, 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 $53.3 million, $42.3 million and $33.7 million for the years ended December 31, 2013, 2012 and 2011, 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 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 non-cancelable 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 and amortization for lease origination costs and customer relationships are recorded as amortization 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 was recognized for the years ended December 31, 2013, 2012, or 2011.
	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 December 31, 2013 and 2012, 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. We utilized the qualitative assessment approach for our 2013 and 2012 annual goodwill impairment evaluation. No impairment loss was recognized for the years ended December 31, 2013, 2012, or 2011.
	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 party 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, which 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 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 are included as a component of interest expense.
	Recoverability of Long-Lived Assets
	The Company reviews its 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 years ended December 31, 2013, 2012, and 2011, no impairment was recognized.
	Derivative Instruments and Hedging Activities
	We reflect all derivative instruments at fair value as either assets or liabilities on the 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 (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. As of December 31, 2013, and 2012, the Company had no derivative instruments outstanding.
	On February 3, 2014, we entered into a $100 million interest rate swap agreement to protect against adverse fluctuations in interest rates by reducing our exposure to variability in cash flow relating to interest payments on $100 million of one month LIBOR variable rate debt, which includes the senior unsecured term loan or the revolving credit facility. The interest rate swap was designated for hedge accounting.
	Revenue Recognition
	All leases are classified as operating leases and minimum rents are recognized on a straight-line basis over the non-cancellable 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. 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.
	A provision for uncollectible accounts is recorded if a receivable balance relating to contractual rent, rent recorded on a straight-line basis, or tenant reimbursements is considered by management to be uncollectible. At December 31, 2013, and 2012, the allowance for doubtful accounts totaled $0.2 million and $0.6 million, respectively.
	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 Black-Scholes option-pricing model and is being amortized on a straight-line basis over the vesting period. 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 and is amortized on a straight-line basis over the vesting period.
	Asset Retirement and Environmental Remediation Obligations
	We record accruals for estimated 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 December 31, 2013, and 2012, the amount included in other liabilities on the consolidated balance sheets was approximately $2.2 million and $2.6 million, respectively.
	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 are generally 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 financial statements for federal income taxes with regards to activities of the REIT and its subsidiary pass-through entities. Any taxable income prior to the completion of the IPO is the responsibility of the Company's prior member. The allocable share of income is included in the income tax returns of the members. 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. Relative deferred tax assets and liabilities arising from temporary differences in financial reporting versus tax reporting are also established as determined by management.
	Deferred income taxes are recognized in certain taxable entities. Deferred income tax is generally 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 not be 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 December 31, 2013, and 2012, the deferred income taxes were not material.
	We currently have no liabilities for uncertain tax positions. The earliest tax year for which we are subject to examination is 2010. Prior to their contribution to our Operating Partnership, our subsidiaries were treated as pass-through entities for tax purposes and the earliest year subject to examination of our subsidiaries is 2010.
	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.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2013
Acquisitions	'
Acquisitions	'
	3. Acquisitions
	In April 2012, the Company paid cash of $2.6 million, net of cash received, to acquire a leasehold interest in two additional locations, DE1 and DE2, through the acquisition of Comfluent, a Denver, Colorado based data center operator. As part of the acquisition, we hired the former owner to assist with management of the buildings. See additional discussion in Note 15.
	In February 2013, the Company acquired land and vacant building in Secaucus, NJ, referred to as NY2, with a book value of $23.4 million, to develop into a data center.

Acquired_Intangible_Assets_and

Acquired Intangible Assets and Liabilities	12 Months Ended
	Dec. 31, 2013
Acquired Intangible Assets and Liabilities	'
Acquired Intangible Assets and Liabilities	'
	4. Acquired Intangible Assets and Liabilities
	During the year ended December 31, 2012, through the acquisition of DE1 and DE2, the Company added $2.9 million of new intangible assets and $0.2 million of new intangible liabilities with a weighted average life of 4.4 years and 0.5 years, respectively. The Company did not acquire new intangible assets or liabilities during the years ended December 31, 2013, and 2011.
	The gross above-market lease value at December 31, 2013, and 2012, was $4.1 million and $6.8 million, respectively, and total accumulated amortization at December 31, 2013, and 2012, was $2.8 million and $4.5 million, respectively. The gross below-market lease value at December 31, 2013, and 2012, was $11.0 million and $18.6 million, respectively, and total accumulated amortization at December 31, 2013, and 2012, was $4.4 million and $10.1 million, respectively. The net effect of amortization of acquired above-market and below-market leases resulted in an increase to rental income of $0.8 million, $1.5 million, and $1.7 million, for the years ended December 31, 2013, 2012, and 2011, respectively. The estimated amortization of acquired below-market leases, net of acquired above-market leases for each of the five succeeding fiscal years, which will be a net increase to rental revenue, is as follows (in thousands):
	Year Ending December 31,
	2014	$	434
	2015		548
	2016		565
	2017		596
	2018		597
	Thereafter		2,590
	Total	$	5,330
	Amortization of all other identified intangible assets was $7.4 million, $18.1 million, and $32.2 million, for the years ended December 31, 2013, 2012, and 2011, respectively. At December 31, 2013, and 2012, the gross intangible value was $24.5 million and $45.7 million, respectively, and the total accumulated amortization balance was $14.8 million and $28.6 million, respectively. The estimated amortization of all other identified intangible assets for each of the five succeeding fiscal years is as follows (in thousands):
	Year Ending December 31,
	2014	$	3,168
	2015		2,071
	2016		1,665
	2017		1,172
	2018		656
	Thereafter		945
	Total	$	9,677

Investment_in_Real_Estate

Investment in Real Estate	12 Months Ended
	Dec. 31, 2013
Investment in Real Estate	'
Investment in Real Estate	'
	5. Investment in Real Estate
	The following is a summary of the properties owned and leased at December 31, 2013 (in thousands):
	Property Name	Location	Land		Buildings and		Leasehold		Construction		Total
					Improvements		Improvements		in Progress		Cost
	SV1	San Jose, CA	$	6,863	$	119,525	$	—	$	3,693	$	130,081
	SV2	Milpitas, CA		5,086		24,202		—		484		29,772
	SV3	Santa Clara, CA		3,972		45,840		—		130		49,942
	SV4	Santa Clara, CA		4,442		86,226		—		680		91,348
	SV5	Santa Clara, CA		2,370		19,986		—		—		22,356
	Santa Clara Campus(1)	Santa Clara, CA		8,173		8,220		—		9,384		25,777
	BO1	Somerville, MA		6,100		77,919		—		2,940		86,959
	NY1	New York, NY		—		—		32,717		46		32,763
	NY2	Secaucus, NJ		386		14,031		—		88,905		103,322
	VA1	Reston, VA		6,903		106,171		—		3,121		116,195
	VA2	Reston, VA		—		—		—		34,030		34,030
	DC1	Washington, DC		—		—		7,417		269		7,686
	CH1	Chicago, IL		5,493		82,011		—		164		87,668
	LA1	Los Angeles, CA		—		—		53,669		2,938		56,607
	LA2	Los Angeles, CA		28,467		122,912		—		10,457		161,836
	MI1	Miami, FL		728		9,964		—		4		10,696
	DE1	Denver, CO		—		—		730		6		736
	DE2	Denver, CO		—		—		685		66		751
	Total		$	78,983	$	717,007	$	95,218	$	157,317	$	1,048,525
	-1
	This campus includes office and light-industrial real estate buildings and land held for development.

Other_Assets

Other Assets	12 Months Ended
	Dec. 31, 2013
Other Assets	'
Other Assets	'
	6. Other Assets
	Our other assets consisted of the following, net of amortization and depreciation, if applicable, as of December 31, 2013, and 2012 (in thousands):
		December 31,		December 31,
		2013		2012
	Deferred leasing costs	$	14,159	$	12,444
	Deferred rent receivable		17,265		15,017
	Deferred financing costs		3,312		2,520
	Corporate furniture, fixtures and equipment		7,346		4,152
	Internal-use software		8,525		2,300
	Other		5,195		6,149
	Total	$	55,802	$	42,582
	Deferred leasing costs are amortized as amortization expense on a straight-line basis over the remaining life of the underlying leases. The estimated amortization of deferred leasing costs for each of the five succeeding fiscal years is as follows (in thousands):
	Year Ending December 31,
	2014	$	4,798
	2015		3,843
	2016		2,132
	2017		1,155
	2018		760
	Thereafter		1,471
	Total	$	14,159

Leases

Leases	12 Months Ended
	Dec. 31, 2013
Leases	'
Leases	'
	7. Leases
	The future minimum lease payments to be received under noncancelable operating leases in effect at December 31, 2013, are as follows (in thousands):
	Year Ending December 31,
	2014	$	129,832
	2015		104,664
	2016		77,789
	2017		52,966
	2018		35,051
	Thereafter		71,141
	Total	$	471,443
	As the lessee, the Company currently leases data center space under noncancelable operating lease agreements at NY1, LA1, DC1, DE1, and DE2, and its headquarters located in Denver, Colorado. The future minimum lease payments to be paid under noncancelable leases in effect at December 31, 2013, are as follows (in thousands):
	Year Ending December 31,
	2014	$	19,028
	2015		19,388
	2016		19,076
	2017		17,641
	2018		15,975
	Thereafter		64,918
	Total	$	156,026

Debt

Debt	12 Months Ended
	Dec. 31, 2013
Debt	'
Debt	'
	8. Debt
	A summary of outstanding indebtedness as of December 31, 2013, and 2012, is as follows (in thousands):
		Interest Rate		Maturity	December 31,		December 31,
				Date	2013		2012
	SV1—Mortgage loan	3.67% and 3.71% at December 31, 2013, and December 31, 2012, respectively		Repaid on January 31, 2014	$	58,250	$	59,750
	Revolving credit facility	2.17% and 2.46% at December 31, 2013, and December 31, 2012, respectively		January 3, 2017		174,250		—
	Total principal outstanding				$	232,500	$	59,750
	Senior Unsecured Term Loan
	On January 31, 2014, our Operating Partnership and certain subsidiaries entered into a $100 million senior unsecured term loan. The senior unsecured 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 senior unsecured term loan ranks pari passu with our revolving credit facility and contains the same financial covenants and other customary restrictive covenants. The borrowings bear interest at a rate per annum equal to LIBOR plus 175 basis points to 265 basis points, each depending on our Operating Partnership's leverage ratio.
	On February 3, 2014, we entered into a $100 million interest rate swap agreement to protect against adverse fluctuation in interest rates by reducing our exposure to variability in cash flow relating to interest payments on $100 million of one month LIBOR variable rate debt, which includes the senior unsecured term loan or the revolving credit facility. The interest rate swap has a five-year term and at CoreSite's current leverage ratio, effectively fixes the senior unsecured term loan interest rate at 3.23%.
	SV1 Mortgage Loan
	As of December 31, 2013, SV1 was subject to a $58.3 million mortgage loan with a maturity date of October 9, 2014. The loan bears variable interest and requires the payment of interest and principal until maturity. The mortgage requires ongoing compliance by us with various covenants including liquidity and net operating income covenants. As of December 31, 2013, we were in compliance with the covenants under the mortgage. On January 31, 2014, we paid off the SV1 Mortgage loan in its entirety using the proceeds from the senior unsecured term loan, discussed above.
	Revolving Credit Facility
	On January 3, 2013, our Operating Partnership and certain subsidiary co-borrowers entered into a second amended and restated senior unsecured revolving credit facility (the "Credit Agreement") with a group of lenders for which KeyBank National Association acts as the administrative agent. The Credit Agreement amended the Operating Partnership's senior secured revolving credit facility, dated December 15, 2011 (the "Prior Facility"), and provides for the release of the properties owned by the Operating Partnership's wholly-owned subsidiaries from the existing liens in favor of the credit facility lenders, with the facility continuing on an unsecured basis and unconditionally guaranteed on a senior unsecured basis by the Company. Our Operating Partnership acts as the parent borrower, and our subsidiaries that own or lease real estate properties, are co-borrowers under the Credit Agreement.
	The Credit Agreement increased the commitment from the Prior Facility of $225.0 million to $355.0 million and extended the initial maturity date of the Prior Facility from December 15, 2014, to January 3, 2017, with a one-time extension option, which, if exercised, would extend the maturity date to January 3, 2018. The exercise of the extension option is subject to the payment of an extension fee equal to 25 basis points of the total commitment under the Credit Agreement at initial maturity and certain other customary conditions. The Credit Agreement contains an accordion feature, which allows our Operating Partnership to increase the total commitment to $500.0 million, under specified circumstances. On June 28, 2013, the borrowers under the Credit Agreement partially exercised the accordion feature to increase the aggregate commitments by $50.0 million. As a result of the accordion exercise, the borrowing capacity increased from $355.0 million to $405.0 million. All other terms of the Credit Agreement remain unchanged.
	Under the Credit Agreement, our Operating Partnership may elect to have borrowings bear interest at a rate per annum equal to (i) LIBOR plus 200 basis points to 275 basis points, or (ii) a base rate plus 100 basis points to 175 basis points, each depending on our Operating Partnership's leverage ratio.
	The total amount available for borrowings under the Credit Agreement is subject to the lesser of the facility amount or the availability calculated based on our unencumbered asset pool. As of December 31, 2013, $174.3 million was borrowed and outstanding and $222.4 million was available for us to borrow under the Credit Agreement. Subsequent to December 31, 2013, CoreSite paid down a portion of the revolving credit facility using the proceeds from the senior unsecured term loan.
	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%. As if December 31, 2013, our leverage ratio was 15.5%.
	•
	a maximum secured debt ratio (defined as total consolidated secured debt to total gross asset value) of 40%. As of December 31, 2013, our secured debt ratio was 3.7%.
	•
	a minimum fixed charge coverage ratio (defined as adjusted consolidated earnings before interest, taxes, depreciation and amortization to consolidated fixed charges) of 1.75 to 1.0. As of December 31, 2013, our fixed charge coverage ratio was 7.2 to 1.0; and
	•
	a maximum unhedged variable rate debt ratio (defined as unhedged variable rate indebtedness to gross asset value) of 30%. As of December 31, 2013, our unhedged variable rate debt ratio was 14.9%.
	As of December 31, 2013, we were in compliance with the covenants under our Credit Agreement.
	Debt Maturities
	The following table summarizes the amount of our outstanding debt, when such debt currently becomes due, including the subsequent impact of the new senior unsecured term loan, payoff of the SV1 mortgage and partial repayment of the revolving credit facility (in thousands, as adjusted for these subsequent events):
	Year Ending December 31,
	2014	$	—
	2015		—
	2016		—
	2017		132,500
	2018		—
	Thereafter		100,000
	Total	$	232,500

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2013
Stockholders' Equity	'
Stockholders' Equity	'
	9. Stockholders' Equity
	At December 31, 2013, 120 million shares were authorized to be issued by CoreSite, of which 100 million shares represent common stock and 20 million represent preferred stock. The Board may, without stockholder approval, classify or reclassify any unissued shares of stock to increase or decrease the authorized number of shares of common stock and preferred stock and to establish the preferences and rights of any preferred stock or other class of series of shares to be issued.
	Common Stock
	At December 31, 2013, we had 21.4 million shares of common stock issued and outstanding. Since IPO, we have issued common stock under our Equity Incentive Plan, in which certain of our employees and outside directors participate in stock-based compensation plans that provide compensation in the form of common stock. Under the Equity Incentive Plan, we received gross proceeds from the exercise of stock options of $0.9 million, $1.6 million, and less than $0.1 million for the years ended December 31, 2013, 2012, and 2011, respectively. Also, we issued shares of common stock as a result of RSA grants, net of forfeitures, and option exercises in the amount of 184,479, 454,879 and 214,142 during the years ended December 31, 2013, 2012, and 2011, respectively. See Note 11 for additional information on the plan.
	On November 15, 2011, 889,610 Operating Partnership units held by third parties were redeemed for common stock of the Company. This redemption was recorded as a $13.8 million reduction to noncontrolling interests in the Operating Partnership and an increase to common stock and additional paid in capital.
	Preferred Stock
	On December 12, 2012, the Company issued an aggregate of 4,600,000 shares of its 7.25% Series A Cumulative Redeemable Preferred Stock, or the series A preferred stock, for net proceeds of $110.6 million. Dividends are cumulative on the series A preferred stock from the date of original issuance in the amount of $1.8125 per share each year, which is equivalent to 7.25% of the $25.00 liquidation preference per share. Dividends on the series A preferred stock are payable quarterly in arrears.
	The series A preferred stock does not have a stated maturity date and is not subject to any sinking fund or mandatory redemption provisions. Upon liquidation, dissolution or winding up, the series A preferred stock will rank senior to the Company common stock with respect to the payment of distributions and other amounts. The Company is not allowed to redeem the series A preferred stock before December 12, 2017, except in limited circumstances to preserve its status as a REIT. On or after December 12, 2017, the Company may, at its option, redeem the series A preferred stock, in whole or in part, at any time or from time to time, for cash at redemption price of $25.00 per share, plus all accrued and unpaid dividends on such series A preferred stock up to but excluding the redemption date. Holders of the series A preferred stock generally have no voting rights except for limited voting rights if the Company fails to pay dividends for six or more quarterly periods (whether or not consecutive) and in certain other circumstances. Upon the occurrence of specified changes of control, as a result of which neither the Company's common stock nor the common securities of the acquiring or surviving entity (or American Depositary Receipts representing such securities) is listed on the New York Stock Exchange, or NYSE, the NYSE Amex Equities or the NASDAQ Stock Market or listed or quoted on a successor exchange or quotation system, each holder of series A preferred stock will have the right (unless, prior to the change of control conversion date specified in the Articles Supplementary governing the series A preferred stock, the Company has provided or provides notice of its election to redeem the series A preferred stock) to convert some or all of the series A preferred stock held by it into a number of shares of the Company's common stock per share of series A preferred stock to be converted equal to the lesser of:
	•
	the quotient obtained by dividing (i) the sum of the $25.00 liquidation preference plus the amount of any accrued and unpaid dividends to, but not including, the change of control conversion date (unless the change of control conversion date is after a record date for a series A preferred stock dividend payment and prior to the corresponding series A preferred stock dividend payment date, in which case no additional amount for such accrued and unpaid dividend will be included in this sum) by (ii) the common stock price, as defined; and
	•
	1.944, or the share cap, subject to certain adjustments;
	subject, in each case, to provisions for the receipt of alternative consideration as described in the Articles Supplementary governing the series A preferred stock. Except in connection with specified change of control transactions, the series A preferred stock is not convertible into or exchangeable for any other property or securities of the Company.
	Dividends
	In 2013, 2012, and 2011, we paid all our dividends in cash. The following summarizes the taxability of our common and preferred stock dividends for the years then ended:
		2013		2012		2011
	Common Stock:
	Ordinary income	$	1.16	$	0.81	$	0.57
	Qualified dividend		—		—		—
	Capital gains		—		—		—
	Return of capital		—		—		—
	Total dividend(1)	$	1.16	$	0.81	$	0.57
	Preferred Stock:
	Ordinary income	$	1.98	$	—	$	—
	Qualified dividend		—		—		—
	Capital gains		—		—		—
	Total dividend(2)	$	1.98		—		—
	-1
	Of the $1.16 taxable dividend in 2013, $0.35 was paid in January 2014. Of the $0.81 taxable dividend in 2012, $0.27 was paid in January 2013. Of the $0.57 taxable dividend in 2011, $0.18 was paid in January 2012.
	-2
	Of the $1.98 taxable dividend in 2013, $0.4531 was paid in January 2014. The 2013 dividend includes a pro rata dividend from and including the original issue date of December 12, 2012. There were no preferred stock dividends in 2012 and 2011.
	In order to comply with the real estate investment trust requirements of the Internal Revenue Code, we are generally required to make common stock distributions (other than capital gain distributions) to our stockholders at least equal to (i) the sum of (a) 90% of our "REIT taxable income" computed without regard to the dividends paid deduction and net capital gains and (b) 90% of the net income (after tax), if any, from foreclosure property, minus (ii) certain excess non-cash income. Our common stock dividend policy is to distribute a percentage of our cash flow to ensure we will meet the distribution requirements of the Internal Revenue Code, while allowing us to retain cash to meet other needs, such as capital improvements and other investment activities.
	Common stock dividends are characterized for federal income tax purposes as ordinary income, qualified dividend, capital gains, non-taxable return of capital or a combination of the four. Common stock dividends that exceed our current and accumulated earnings and profits (calculated for tax purposes) constitute a return of capital rather than a dividend and generally reduce the stockholder's basis in the common stock. To the extent that a dividend exceeds both current and accumulated earnings and profits and the stockholder's basis in the common stock, it will generally be treated as a gain from the sale or exchange of that stockholder's common stock. At the beginning of each year, we notify our stockholders of the taxability of the common stock dividends paid during the preceding year.
	Pursuant to the terms of our preferred stock, we are restricted from declaring or paying any dividend with respect to our common stock unless and until all cumulative dividends with respect to the preferred stock have been paid and sufficient funds have been set aside for dividends that have been declared for the relevant dividend period with respect to the preferred stock.
	Our tax return for the year ended December 31, 2013 has not been filed. The taxability information presented for our dividends paid in 2013 is based upon management's estimate.

Noncontrolling_Interests_Opera

Noncontrolling Interests - Operating Partnership	12 Months Ended
	Dec. 31, 2013
Noncontrolling Interests - Operating Partnership	'
Noncontrolling Interests - Operating Partnership	'
	10. 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. Since September 28, 2011, the current holders of Common Operating Partnership units have been eligible to have the Common Operating Partnership units redeemed for our common stock on a one-for-one basis or cash, at our option.
	The following table shows the ownership interest in the Operating Partnership as of December 31, 2013, and 2012:
		December 31, 2013					December 31, 2012
		Number of Units		Percentage of Total			Number of Units		Percentage of Total
	The Company		20,896,685		45.2	%		20,610,523		44.8	%
	Noncontrolling interests consist of:
	Common units held by third parties		25,275,390		54.6	%		25,275,390		55	%
	Incentive units held by employees		85,457		0.2	%		78,319		0.2	%
	Total		46,257,532		100	%		45,964,232		100	%
	For each share of common stock issued by the Company, the Operating Partnership issues an equivalent Common Operating Partnership unit to the Company. During the year ended December 31, 2013, the Company issued 286,964 shares of common stock related to employee compensation arrangements and therefore an equivalent number of Common Operating Partnership units were issued to the Company by the Operating Partnership. Additionally, during the year ended December 31, 2013, Operating Partnership units of 7,138 were issued to employees upon their vesting in the incentive unit awards.
	Holders of Common Operating Partnership units of record as of March 28, 2013, June 28, 2013, and September 30, 2013, received quarterly distributions of $0.27 per unit payable in correlation with declared dividends on common shares. Holders of Common Operating Partnership units of record as of December 31, 2013, received quarterly distributions of $0.35 per unit payable in correlation with declared dividends on common shares.
	On December 12, 2012, the Operating Partnership issued 4.6 million Preferred Operating Partnership units to the Company in connection with our issuance of Series A Cumulative Preferred Stock. The Preferred Operating Partnership units rank senior to the Common Operating Partnership units held by the Company and noncontrolling interests.
	The redemption value of the noncontrolling interests at December 31, 2013, was $816.4 million based on the closing price of the Company's stock of $32.19 on that date.

Equity_Incentive_Plan

Equity Incentive Plan	12 Months Ended
	Dec. 31, 2013
Equity Incentive Plan	'
Equity Incentive Plan	'
	11. Equity Incentive Plan
	In connection with our IPO, the Company's Board of Directors adopted the 2010 Equity Incentive Plan (as amended, the "2010 Plan"). The 2010 Plan is administered by the Board of Directors, or the plan administrator. Awards issuable under the 2010 Plan include common stock, stock options, restricted stock, stock appreciation rights, dividend equivalents and other incentive awards. Following approval by the Board of Directors on March 30, 2013, our stockholders on May 22, 2013, approved the amendment and restatement of the 2010 Plan which, among other things, increased the number of shares of common stock authorized for issuance by 3,000,000 shares. 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, or an award is settled in cash without the delivery of shares of common stock to the participant, 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 optioned, granted or 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 December 31, 2013, 3,686,242 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 at 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 being amortized on a straight-line basis over the vesting periods.
	The following table sets forth the stock option activity under the 2010 Plan for the years ended December 31, 2013, 2012, and 2011:
		Number of			Weighted			Weighted Average		Aggregate Intrinsic
		Shares Subject			Average			Remaining		Value
		to Option			Exercise Price			Contractual
								Term
	Options outstanding, December 31, 2010		587,555			16		9.7 years		$—
	Granted		543,380			15.27
	Forfeited		(122,848	)		15.8
	Expired		(8,074	)		16
	Exercised		(1,962	)		16				Less than $0.1 million
	Options outstanding, December 31, 2011		998,051		$	15.63		8.9 years		$2.2 million
	Granted		236,893			23.87
	Forfeited		(119,723	)		16.62
	Expired		(156	)		16
	Exercised		(97,870	)		16.04				$0.8 million
	Options outstanding, December 31, 2012		1,017,195			17.25		8.2 years		$10.6 million
	Granted		209,268			32.5
	Forfeited		(37,232	)		23
	Expired		(535	)		34.82
	Exercised		(54,781	)		16.86				$1.0 million
	Options outstanding, December 31, 2013		1,133,915			19.89		7.6 years		$14.0 million
	Exercisable at December 31,
	2011		130,942		$	16		8.7 years		$0.2 million
	2012		287,036		$	15.74		7.9 years		$3.4 million
	2013		498,176		$	16.51		7.1 years		$7.8 million
	The following table sets forth the number of shares subject to option that are unvested as of December 31, 2013, 2012, and 2011, and the fair value of these options at the grant date:
		Number of			Weighted
		Shares Subject			Average Fair
		to Option			Value at Grant Date
	Unvested balance, December 31, 2010		587,555			4.95
	Granted		543,380			4.89
	Forfeited		(122,848	)		4.93
	Vested		(140,978	)		4.92
	Unvested balance, December 31, 2011		867,109		$	4.92
	Granted		236,893			7.76
	Forfeited		(119,723	)		5.24
	Vested		(254,120	)		4.96
	Unvested balance, December 31, 2012		730,159		$	5.7
	Granted		209,268			10.01
	Forfeited		(37,232	)		7.21
	Vested		(266,456	)		5.54
	Unvested balance, December 31, 2013		635,739		$	7.1
	As of December 31, 2013, total unearned compensation on options was approximately $3.3 million, and the weighted average vesting period was 2.0 years. The fair value of each option award is estimated on the date of grant using a Black-Scholes option valuation model. As the Company has been a publicly traded company only since September 28, 2010, expected volatilities used in the Black-Scholes model are based on the historical volatility of a group of comparable REITs. We utilize the simplified method of estimating the term for options granted due to the lack of historical exercise data necessary to provide a reasonable basis upon which to estimate the term. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. The following table summarizes the assumptions used to value the stock options granted during the years ended December 31, 2013, 2012, and 2011:
		2013			2012			2011
	Expected term (in years)		6.25			6.25			6.25
	Expected volatility		43.86	%		44.08	%		43.07	%
	Expected annual dividend		3.33	%		3	%		3.41	%
	Risk-free rate		1.26	%		1.56	%		2.76	%
	Restricted Awards
	During the years ended December 31, 2013, 2012, and 2011, the Company issued 188,710, 405,608 and 263,393 shares of restricted stock, respectively, which had values of $6.1 million, $9.9 million, and $4.0 million, respectively, on the grant date. Also during the years ended December 31, 2013, 2012, and 2011, the Company issued 5,592, 7,172 and 10,080 restricted stock units or RSUs, respectively, which each grant had values of $0.2 million on the grant date. The principal difference between these instruments is that RSUs are not shares of the Company's 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 awards will be amortized on a straight-line basis to expense over the vesting period. The following table sets forth the number of unvested restricted awards and the weighted average fair value of these awards at the date of grant:
		Restricted			Weighted
		Awards			Average Fair
					Value at Grant Date
	Unvested balance, December 31, 2010		195,437			15.98
	Granted		273,473			15.19
	Forfeited		(51,213	)		15.81
	Vested		(74,466	)		16.1
	Unvested balance, December 31, 2011		343,231			15.35
Granted		412,780			24.59
Forfeited		(48,599	)		18.26
Vested		(108,717	)		15.46
Unvested balance, December 31, 2012		598,695		$	21.37
Granted		194,302			32.43
Forfeited		(58,199	)		28.44
Vested		(239,647	)		20.96
Unvested balance, December 31, 2013		495,151		$	25.08
As of December 31, 2013, total unearned compensation on restricted awards was approximately $9.0 million, and the weighted average vesting period was 2.1 years.
Operating Partnership Units
In connection with the IPO, we issued 25,883 Operating Partnership units, which were fair valued at $15.98 per unit or $0.4 million in total. The Operating Partnership units will be amortized on a straight-line basis to expense over the vesting period. As of December 31, 2013, 24,392 units have vested, 1,491 were forfeited and there were no unvested units. These units have the same rights as holders of Common Operating Partnership units.

Earnings_Per_Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2013
Earnings Per Share	'
Earnings Per Share	'
	12. Earnings Per Share
	Basic income (loss) per share is calculated by dividing the net income (loss) attributable to common shares by the weighted average number of common shares outstanding during the period. Diluted income (loss) per share adjusts basic income (loss) per share for the effects of potentially dilutive common shares, if the effect is not antidilutive. Potentially dilutive common shares consist of shares issuable under our equity-based compensation plan and Operating Partnership units.
		Twelve Months Ended December 31,
		2013		2012		2011
	Net income (loss) attributable to common shares	$	10,503	$	4,608	$	(4,611	)
	Weighted average common shares outstanding—basic		20,826,622		20,537,946		19,609,375
	Effect of potentially dilutive common shares:
	Stock options		383,743		211,222		—
	Unvested restricted awards		292,847		243,122		—
	Weighted average common shares outstanding—diluted		21,503,212		20,992,290		19,609,375
	Net income (loss) per share attributable to common shares
	Basic	$	0.5	$	0.22	$	(0.24	)
	Diluted	$	0.49	$	0.22	$	(0.24	)
	In the calculations above, we have excluded potentially dilutive securities of 169,875, 153,972 and 1,341,282 for the years ended December 31, 2013, 2012, and 2011, respectively, as their effect would have been antidilutive.

Estimated_Fair_Value_of_Financ

Estimated Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2013
Estimated Fair Value of Financial Instruments	'
Estimated Fair Value of Financial Instruments	'
	13. 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, restricted cash, accounts and other receivables, revolving credit facility, mortgage loans payable, interest payable and accounts payable. The carrying values of cash and cash equivalents, restricted cash, accounts and other receivables, interest payable and accounts payable approximate fair values due to the short-term nature of these financial instruments.
	The total balance of our mortgage loan payable and revolving credit facility was $232.5 million and $59.8 million as of December 31, 2013 and 2012, respectively, with a fair value that approximated book value at both periods, based on Level 3 inputs from the fair value hierarchy. Under the discounted cash flow method, the fair values of mortgage notes payable and the revolving credit facility are based on the Company's assumptions of interest rates and terms available incorporating the Company's credit risk.

Related_Party_Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2013
Related Party Transactions	'
Related Party Transactions	'
	14. Related Party Transactions
	We lease 1,520 net rentable square feet of space at VA1 and 375 net rentable square feet of space at LA1 to affiliates of The Carlyle Group (Carlyle). Affiliates of Carlyle own a 54.6% common interest in the Operating Partnership. Rental revenue from these leases was $0.4 million, $0.3 million, and $0.2 million for the years ended December 31, 2013, 2012, and 2011, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies	'
Commitments and Contingencies	'
	15. Commitments and Contingencies
	Our properties require periodic investments of capital for general capital improvements and for tenant related capital expenditures. Additionally, the Company enters into various construction and equipment contracts with third parties for the development of our properties. At December 31, 2013, we had open commitments related to construction contracts of approximately $28.9 million.
	Additionally, the Company has commitments related to telecommunications capacity used to connect data centers located within the same market or geographical area and power usage. At December 31, 2013, we had open commitments related to these contracts of approximately $5.6 million.
	We have agreed with each of the Funds or their affiliates that have directly or indirectly contributed their interests in the properties in our portfolio to our operating partnership that if we directly or indirectly sell, convey, transfer or otherwise dispose of all or any portion of these interests in a taxable transaction, we will make an interest-free loan to the contributors in an amount equal to the contributor's tax liabilities, based on an assumed tax rate, with respect to built-in-gains generated from the initial contribution. These tax protection provisions apply for a period expiring on the earliest of (i) the seventh anniversary of the completion of our IPO and (ii) the date on which these contributors (or certain transferees) dispose in certain taxable transactions of 90% of the operating partnership units that were issued to them in connection with the contribution of these properties.
	As part of our 2012 acquisition of Comfluent, a Denver, Colorado based data center operator, the former Comfluent owner was hired and is compensated based upon successfully renewing and increasing revenue from the customer base that existed at the date of acquisition. We currently estimate that this amount is $8.0 million, assuming all customers are renewed beyond January 2015. We currently have $1.2 million accrued as a leasing commission related to those customers that have been renewed as of December 31, 2013.
	Effective January 24, 2014, Jarrett Appleby, our former Chief Operating Officer, separated from the Company. In accordance with Mr. Appleby's employment agreement, we estimated $0.9 million of expense during the first quarter of 2014 associated with cash severance benefits and acceleration of share-based compensation.
	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 matters to which we currently are a party, the ultimate disposition of any such matter will not result in a material adverse effect on us.

Quarterly_Financial_Informatio

Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information (unaudited)	'
Quarterly Financial Information (unaudited)	'
	16. Quarterly Financial Information (unaudited)
	The table below reflects the selected quarterly information for the years ended December 31, 2013, and 2012 (in thousands except share data):
		Three Months Ended
		December 31,		September 30,		June 30,		March 31,
		2013		2013		2013		2013
	Revenue	$	61,440	$	60,635	$	57,667	$	55,091
	Operating income		9,740		9,259		8,866		6,805
	Net income		9,029		8,509		7,879		6,195
	Net income attributable to common shares		3,135		2,901		2,618		1,849
	Net income per share attributable to common shares—basic	$	0.15	$	0.14	$	0.13	$	0.08
	Net income per share attributable to common shares—diluted	$	0.15	$	0.14	$	0.12	$	0.08
		Three Months Ended
		December 31,		September 30,		June 30,		March 31,
		2012		2012		2012		2012
	Revenue	$	55,252	$	53,762	$	50,636	$	47,284
	Operating income		5,936		5,059		3,814		2,234
	Net income		4,578		2,947		1,848		1,343
	Net income attributable to common shares		1,862		1,320		826		600
	Net income per share attributable to common shares—basic	$	0.09	$	0.06	$	0.04	$	0.03
	Net income per share attributable to common shares—diluted	$	0.09	$	0.06	$	0.04	$	0.03

Schedule_III_Real_Estate_and_A

Schedule III Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2013
Schedule III Real Estate and Accumulated Depreciation	'
Schedule III Real Estate and Accumulated Depreciation	'
	Schedule III
	Real Estate and Accumulated Depreciation
	December 31, 2013
														Gross Amount Carried at
							Initial Cost					Costs		December 31, 2013						Accumulated
												Capitalized								Depreciation
												Subsequent								at
												to								December 31,		Year
												Acquisition								2013		Acquired
																						or
	Property	Location		Encumbrances			Land			Building and				Land		Building and		Total				Leased
	Name									Improvements						Improvements
		(In thousands)
	SV1	San Jose, CA		$	58,250		$	6,863		$	91,719	$	31,499	$	6,863	$	123,218	$	130,081	$	11,787		2010
	SV2	Milpitas, CA			—			5,086			5,046		19,640		5,086		24,686		29,772		10,454		2006
	SV3	Santa Clara, CA			—			3,972			3,482		42,488		3,972		45,970		49,942		15,972		2007
	SV4	Santa Clara, CA			—			4,442			3,716		83,190		4,442		86,906		91,348		9,079		2007
	SV5	Santa Clara, CA			—			2,370			—		19,986		2,370		19,986		22,356		80		2007
	Santa Clara Campus	Santa Clara, CA			—			9,116			9,240		7,421		8,173		17,604		25,777		1,917		2007
	BO1	Somerville, MA			—			6,100			26,748		54,111		6,100		80,859		86,959		24,257		2007
	NY1	New York, NY			—			—			—		32,763		—		32,763		32,763		11,241		2007
	NY2	Secaucus, NJ			—			4,952			18,408		79,962		386		102,936		103,322		80		2013
	VA1	Reston, VA			—			6,903			32,939		76,353		6,903		109,292		116,195		26,007		2007
	VA2	Reston, VA			—			5,197			—		28,833		—		34,030		34,030		—		2007
	DC1	Washington, DC			—			—			4,797		2,889		—		7,686		7,686		2,124		2010
	CH1	Chicago, IL			—			5,493			49,522		32,653		5,493		82,175		87,668		10,727		2010
	LA1	Los Angeles, CA			—			—			41,099		15,508		—		56,607		56,607		13,681		2010
	LA2	Los Angeles, CA			—			28,467			94,114		39,255		28,467		133,369		161,836		16,516		2010
	MI1	Miami, FL			—			728			9,325		643		728		9,968		10,696		1,440		2010
	DE1	Denver, CO			—			—			37		699		—		736		736		164		2012
	DE2	Denver, CO			—			—			4		747		—		751		751		178		2012
		Total		$	58,250		$	89,689		$	390,196	$	568,640	$	78,983	$	969,542	$	1,048,525	$	155,704
	The aggregate cost of the total properties for federal income tax purposes was approximately $947.3 million (unaudited) at December 31, 2013.
	Schedule III
	Real Estate and Accumulated Depreciation
	December 31, 2013
	The following table reconciles the historical cost and accumulated depreciation of the CoreSite Realty Corporation properties for the years ended December 31, 2013, 2012, and 2011:
		2013			2012			2011
		(In thousands)
	Property
	Balance, beginning of period	$	829,508		$	741,981		$	624,122
	Additions—property acquisitions		23,360			—			—
	Additions—improvements		195,657			87,527			117,859
	Balance, end of period	$	1,048,525		$	829,508		$	741,981
	Accumulated Depreciation
	Balance, beginning of period	$	105,433		$	64,428		$	32,943
	Additions—depreciation, net of disposals		50,271			41,005			31,485
	Balance, end of period	$	155,704		$	105,433		$	64,428

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Principles of Consolidation and Basis of Presentation	'
	Principles of Consolidation and Basis of Presentation
	The accompanying consolidated financial statements have been prepared by management in accordance with U.S. generally accepted accounting principles ("GAAP"). Intercompany balances and transactions have been eliminated in these consolidated financial statements. The Company reviewed subsequent events through the issuance date for inclusion in these consolidated financial statements.
Use of Estimates	'
	Use of Estimates
	The preparation of 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 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
	Office, light industrial and other revenue, included within the consolidated statements of operations for the years ended December 31, 2012, and 2011, have been reclassified to conform to the 2013 financial statement presentation. In addition, certain other immaterial amounts included in the consolidated financial statements for 2012 and 2011 have been reclassified to conform to the 2013 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 the 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 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 $4.4 million, $1.8 million and $1.6 million for the years ended December 31, 2013, 2012, and 2011, 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 $53.3 million, $42.3 million and $33.7 million for the years ended December 31, 2013, 2012 and 2011, 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 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 non-cancelable 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 and amortization for lease origination costs and customer relationships are recorded as amortization 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 was recognized for the years ended December 31, 2013, 2012, or 2011.
	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 December 31, 2013 and 2012, 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. We utilized the qualitative assessment approach for our 2013 and 2012 annual goodwill impairment evaluation. No impairment loss was recognized for the years ended December 31, 2013, 2012, or 2011.
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 party 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, which 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 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 are included as a component of interest expense.
Recoverability of Long-Lived Assets	'
	Recoverability of Long-Lived Assets
	The Company reviews its 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 years ended December 31, 2013, 2012, and 2011, no impairment 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 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 (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. As of December 31, 2013, and 2012, the Company had no derivative instruments outstanding.
	On February 3, 2014, we entered into a $100 million interest rate swap agreement to protect against adverse fluctuations in interest rates by reducing our exposure to variability in cash flow relating to interest payments on $100 million of one month LIBOR variable rate debt, which includes the senior unsecured term loan or the revolving credit facility. The interest rate swap was designated for hedge accounting.
Revenue Recognition	'
	Revenue Recognition
	All leases are classified as operating leases and minimum rents are recognized on a straight-line basis over the non-cancellable 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. 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.
	A provision for uncollectible accounts is recorded if a receivable balance relating to contractual rent, rent recorded on a straight-line basis, or tenant reimbursements is considered by management to be uncollectible. At December 31, 2013, and 2012, the allowance for doubtful accounts totaled $0.2 million and $0.6 million, respectively.
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 Black-Scholes option-pricing model and is being amortized on a straight-line basis over the vesting period. 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 and 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 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 December 31, 2013, and 2012, the amount included in other liabilities on the consolidated balance sheets was approximately $2.2 million and $2.6 million, respectively.
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 are generally 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 financial statements for federal income taxes with regards to activities of the REIT and its subsidiary pass-through entities. Any taxable income prior to the completion of the IPO is the responsibility of the Company's prior member. The allocable share of income is included in the income tax returns of the members. 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. Relative deferred tax assets and liabilities arising from temporary differences in financial reporting versus tax reporting are also established as determined by management.
	Deferred income taxes are recognized in certain taxable entities. Deferred income tax is generally 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 not be 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 December 31, 2013, and 2012, the deferred income taxes were not material.
	We currently have no liabilities for uncertain tax positions. The earliest tax year for which we are subject to examination is 2010. Prior to their contribution to our Operating Partnership, our subsidiaries were treated as pass-through entities for tax purposes and the earliest year subject to examination of our subsidiaries is 2010.
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_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
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

Acquired_Intangible_Assets_and1

Acquired Intangible Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2013
Acquired Intangible Assets and Liabilities	'
Schedule of estimated amortization of acquired below-market leases, net of acquired above-market leases	'
	The estimated amortization of acquired below-market leases, net of acquired above-market leases for each of the five succeeding fiscal years, which will be a net increase to rental revenue, is as follows (in thousands):
	Year Ending December 31,
	2014	$	434
	2015		548
	2016		565
	2017		596
	2018		597
	Thereafter		2,590
	Total	$	5,330
Schedule of estimated amortization of all other identified intangible assets	'
	The estimated amortization of all other identified intangible assets for each of the five succeeding fiscal years is as follows (in thousands):
	Year Ending December 31,
	2014	$	3,168
	2015		2,071
	2016		1,665
	2017		1,172
	2018		656
	Thereafter		945
	Total	$	9,677

Investment_in_Real_Estate_Tabl

Investment in Real Estate (Tables)	12 Months Ended
	Dec. 31, 2013
Investment in Real Estate	'
Summary of properties owned and leased	'
	The following is a summary of the properties owned and leased at December 31, 2013 (in thousands):
	Property Name	Location	Land		Buildings and		Leasehold		Construction		Total
					Improvements		Improvements		in Progress		Cost
	SV1	San Jose, CA	$	6,863	$	119,525	$	—	$	3,693	$	130,081
	SV2	Milpitas, CA		5,086		24,202		—		484		29,772
	SV3	Santa Clara, CA		3,972		45,840		—		130		49,942
	SV4	Santa Clara, CA		4,442		86,226		—		680		91,348
	SV5	Santa Clara, CA		2,370		19,986		—		—		22,356
	Santa Clara Campus(1)	Santa Clara, CA		8,173		8,220		—		9,384		25,777
	BO1	Somerville, MA		6,100		77,919		—		2,940		86,959
	NY1	New York, NY		—		—		32,717		46		32,763
	NY2	Secaucus, NJ		386		14,031		—		88,905		103,322
	VA1	Reston, VA		6,903		106,171		—		3,121		116,195
	VA2	Reston, VA		—		—		—		34,030		34,030
	DC1	Washington, DC		—		—		7,417		269		7,686
	CH1	Chicago, IL		5,493		82,011		—		164		87,668
	LA1	Los Angeles, CA		—		—		53,669		2,938		56,607
	LA2	Los Angeles, CA		28,467		122,912		—		10,457		161,836
	MI1	Miami, FL		728		9,964		—		4		10,696
	DE1	Denver, CO		—		—		730		6		736
	DE2	Denver, CO		—		—		685		66		751
	Total		$	78,983	$	717,007	$	95,218	$	157,317	$	1,048,525
	-1
	This campus includes office and light-industrial real estate buildings and land held for development.

Other_Assets_Tables

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2013
Other Assets	'
Schedule of other assets	'
	Our other assets consisted of the following, net of amortization and depreciation, if applicable, as of December 31, 2013, and 2012 (in thousands):
		December 31,		December 31,
		2013		2012
	Deferred leasing costs	$	14,159	$	12,444
	Deferred rent receivable		17,265		15,017
	Deferred financing costs		3,312		2,520
	Corporate furniture, fixtures and equipment		7,346		4,152
	Internal-use software		8,525		2,300
	Other		5,195		6,149
	Total	$	55,802	$	42,582
Schedule of estimated amortization of deferred leasing costs	'
	The estimated amortization of deferred leasing costs for each of the five succeeding fiscal years is as follows (in thousands):
	Year Ending December 31,
	2014	$	4,798
	2015		3,843
	2016		2,132
	2017		1,155
	2018		760
	Thereafter		1,471
	Total	$	14,159

Leases_Tables

Leases (Tables)	12 Months Ended
	Dec. 31, 2013
Leases	'
Schedule of future minimum lease payments to be received under noncancelable operating leases	'
	The future minimum lease payments to be received under noncancelable operating leases in effect at December 31, 2013, are as follows (in thousands):
	Year Ending December 31,
	2014	$	129,832
	2015		104,664
	2016		77,789
	2017		52,966
	2018		35,051
	Thereafter		71,141
	Total	$	471,443
Schedule of future minimum lease payments to be paid under noncancelable leases	'
	The future minimum lease payments to be paid under noncancelable leases in effect at December 31, 2013, are as follows (in thousands):
	Year Ending December 31,
	2014	$	19,028
	2015		19,388
	2016		19,076
	2017		17,641
	2018		15,975
	Thereafter		64,918
	Total	$	156,026

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2013
Debt	'
Summary of outstanding indebtedness	'
	A summary of outstanding indebtedness as of December 31, 2013, and 2012, is as follows (in thousands):
		Interest Rate		Maturity	December 31,		December 31,
				Date	2013		2012
	SV1—Mortgage loan	3.67% and 3.71% at December 31, 2013, and December 31, 2012, respectively		Repaid on January 31, 2014	$	58,250	$	59,750
	Revolving credit facility	2.17% and 2.46% at December 31, 2013, and December 31, 2012, respectively		January 3, 2017		174,250		—
	Total principal outstanding				$	232,500	$	59,750
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, when such debt currently becomes due, including the subsequent impact of the new senior unsecured term loan, payoff of the SV1 mortgage and partial repayment of the revolving credit facility (in thousands, as adjusted for these subsequent events):
	Year Ending December 31,
	2014	$	—
	2015		—
	2016		—
	2017		132,500
	2018		—
	Thereafter		100,000
	Total	$	232,500

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2013
Stockholders' Equity	'
Summary of taxability of common and preferred stock dividends	'
		2013		2012		2011
	Common Stock:
	Ordinary income	$	1.16	$	0.81	$	0.57
	Qualified dividend		—		—		—
	Capital gains		—		—		—
	Return of capital		—		—		—
	Total dividend(1)	$	1.16	$	0.81	$	0.57
	Preferred Stock:
	Ordinary income	$	1.98	$	—	$	—
	Qualified dividend		—		—		—
	Capital gains		—		—		—
	Total dividend(2)	$	1.98		—		—
	-1
	Of the $1.16 taxable dividend in 2013, $0.35 was paid in January 2014. Of the $0.81 taxable dividend in 2012, $0.27 was paid in January 2013. Of the $0.57 taxable dividend in 2011, $0.18 was paid in January 2012.
	-2
	Of the $1.98 taxable dividend in 2013, $0.4531 was paid in January 2014. The 2013 dividend includes a pro rata dividend from and including the original issue date of December 12, 2012. There were no preferred stock dividends in 2012 and 2011.

Noncontrolling_Interests_Opera1

Noncontrolling Interests - Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2013
Noncontrolling Interests - Operating Partnership	'
Schedule of ownership interest in the Operating Partnership	'
		December 31, 2013					December 31, 2012
		Number of Units		Percentage of Total			Number of Units		Percentage of Total
	The Company		20,896,685		45.2	%		20,610,523		44.8	%
	Noncontrolling interests consist of:
	Common units held by third parties		25,275,390		54.6	%		25,275,390		55	%
	Incentive units held by employees		85,457		0.2	%		78,319		0.2	%
	Total		46,257,532		100	%		45,964,232		100	%

Equity_Incentive_Plan_Tables

Equity Incentive Plan (Tables)	12 Months Ended
	Dec. 31, 2013
Equity Incentive Plan	'
Schedule of stock option activity	'
		Number of			Weighted			Weighted Average		Aggregate Intrinsic
		Shares Subject			Average			Remaining		Value
		to Option			Exercise Price			Contractual
								Term
	Options outstanding, December 31, 2010		587,555			16		9.7 years		$—
	Granted		543,380			15.27
	Forfeited		(122,848	)		15.8
	Expired		(8,074	)		16
	Exercised		(1,962	)		16				Less than $0.1 million
	Options outstanding, December 31, 2011		998,051		$	15.63		8.9 years		$2.2 million
	Granted		236,893			23.87
	Forfeited		(119,723	)		16.62
	Expired		(156	)		16
	Exercised		(97,870	)		16.04				$0.8 million
	Options outstanding, December 31, 2012		1,017,195			17.25		8.2 years		$10.6 million
	Granted		209,268			32.5
	Forfeited		(37,232	)		23
	Expired		(535	)		34.82
	Exercised		(54,781	)		16.86				$1.0 million
	Options outstanding, December 31, 2013		1,133,915			19.89		7.6 years		$14.0 million
	Exercisable at December 31,
	2011		130,942		$	16		8.7 years		$0.2 million
	2012		287,036		$	15.74		7.9 years		$3.4 million
	2013		498,176		$	16.51		7.1 years		$7.8 million
Schedule of unvested shares subject to option	'
		Number of			Weighted
		Shares Subject			Average Fair
		to Option			Value at Grant Date
	Unvested balance, December 31, 2010		587,555			4.95
	Granted		543,380			4.89
	Forfeited		(122,848	)		4.93
	Vested		(140,978	)		4.92
	Unvested balance, December 31, 2011		867,109		$	4.92
	Granted		236,893			7.76
	Forfeited		(119,723	)		5.24
	Vested		(254,120	)		4.96
	Unvested balance, December 31, 2012		730,159		$	5.7
	Granted		209,268			10.01
	Forfeited		(37,232	)		7.21
	Vested		(266,456	)		5.54
	Unvested balance, December 31, 2013		635,739		$	7.1
Summary of assumptions used to value the stock options granted	'
		2013			2012			2011
	Expected term (in years)		6.25			6.25			6.25
	Expected volatility		43.86	%		44.08	%		43.07	%
	Expected annual dividend		3.33	%		3	%		3.41	%
	Risk-free rate		1.26	%		1.56	%		2.76	%
Schedule of restricted awards	'
		Restricted			Weighted
		Awards			Average Fair
					Value at Grant Date
	Unvested balance, December 31, 2010		195,437			15.98
	Granted		273,473			15.19
	Forfeited		(51,213	)		15.81
	Vested		(74,466	)		16.1
	Unvested balance, December 31, 2011		343,231			15.35
	Granted		412,780			24.59
	Forfeited		(48,599	)		18.26
	Vested		(108,717	)		15.46
	Unvested balance, December 31, 2012		598,695		$	21.37
	Granted		194,302			32.43
	Forfeited		(58,199	)		28.44
	Vested		(239,647	)		20.96
	Unvested balance, December 31, 2013		495,151		$	25.08

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2013
Earnings Per Share	'
Schedule of potentially dilutive securities excluded in the calculation of basic and diluted income (loss) per share	'
		Twelve Months Ended December 31,
		2013		2012		2011
	Net income (loss) attributable to common shares	$	10,503	$	4,608	$	(4,611	)
	Weighted average common shares outstanding—basic		20,826,622		20,537,946		19,609,375
	Effect of potentially dilutive common shares:
	Stock options		383,743		211,222		—
	Unvested restricted awards		292,847		243,122		—
	Weighted average common shares outstanding—diluted		21,503,212		20,992,290		19,609,375
	Net income (loss) per share attributable to common shares
	Basic	$	0.5	$	0.22	$	(0.24	)
	Diluted	$	0.49	$	0.22	$	(0.24	)

Quarterly_Financial_Informatio1

Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Information (unaudited)	'
Schedule of selected quarterly information	'
	The table below reflects the selected quarterly information for the years ended December 31, 2013, and 2012 (in thousands except share data):
		Three Months Ended
		December 31,		September 30,		June 30,		March 31,
		2013		2013		2013		2013
	Revenue	$	61,440	$	60,635	$	57,667	$	55,091
	Operating income		9,740		9,259		8,866		6,805
	Net income		9,029		8,509		7,879		6,195
	Net income attributable to common shares		3,135		2,901		2,618		1,849
	Net income per share attributable to common shares—basic	$	0.15	$	0.14	$	0.13	$	0.08
	Net income per share attributable to common shares—diluted	$	0.15	$	0.14	$	0.12	$	0.08
		Three Months Ended
		December 31,		September 30,		June 30,		March 31,
		2012		2012		2012		2012
	Revenue	$	55,252	$	53,762	$	50,636	$	47,284
	Operating income		5,936		5,059		3,814		2,234
	Net income		4,578		2,947		1,848		1,343
	Net income attributable to common shares		1,862		1,320		826		600
	Net income per share attributable to common shares—basic	$	0.09	$	0.06	$	0.04	$	0.03
	Net income per share attributable to common shares—diluted	$	0.09	$	0.06	$	0.04	$	0.03

Organization_Details

Organization (Details) (Common Shares, Operating partnership)	Dec. 31, 2013
Common Shares | Operating partnership	'
Organization	'
Percentage of ownership interests held by the entity	45.20%

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investments in Real Estate	'	'	'
Capitalized interest costs	$4.40	$1.80	$1.60
Depreciation expense	$53.30	$42.30	$33.70
Buildings | Minimum	'	'	'
Investments in Real Estate	'	'	'
Useful lives	'27 years	'	'
Buildings | 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_Account4

Summary of Significant Accounting Policies (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	item	item
Summary of Significant Accounting Policies	'	'	'
Impairment loss related to goodwill	$0	$0	$0
Goodwill	41,191,000	41,191,000	'
Acquisition of Investment in Real Estate	'	'	'
Impairment loss related to intangible assets	0	0	0
Recoverability of Long-Lived Assets	'	'	'
Impairment of long-lived assets	$0	$0	$0
Derivative Instruments and Hedging Activities	'	'	'
Number of derivative instruments outstanding	0	0	'

Summary_of_Significant_Account5

Summary of Significant Accounting Policies (Details 3) (Interest rate swap, Subsequent event, Designated as hedging instrument, USD $)	0 Months Ended
In Millions, unless otherwise specified	Feb. 03, 2014
Derivative instruments and hedging activities disclosures	'
Notional amount of interest rate derivatives	100
Amount borrowed under term loan or revolving credit facility	100
LIBOR	'
Derivative instruments and hedging activities disclosures	'
Reference rate	'one month LIBOR

Summary_of_Significant_Account6

Summary of Significant Accounting Policies (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Revenue Recognition	'	'
Allowance for doubtful accounts (in dollars)	$159,000	$625,000
Asset Retirement and Environmental Remediation Obligations	'	'
Asset retirement and environmental remediation obligations	2,200,000	2,600,000
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	'

Summary_of_Significant_Account7

Summary of Significant Accounting Policies (Details 5)	12 Months Ended
	Dec. 31, 2013
	item
Concentration of Credit Risks	'
Number of off-balance-sheet concentrations of credit risk	0
Segment information	'
Number of reportable segments	1

Acquisitions_Details

Acquisitions (Details) (USD $)	Feb. 28, 2013	Apr. 30, 2012
In Millions, unless otherwise specified		Comfluent
		item
Acquisitions	'	'
Cash paid, net of cash received towards acquisition	'	$2.60
Book value of acquired land and vacant building	$23.40	'
Number of leased locations	'	2

Acquired_Intangible_Assets_and2

Acquired Intangible Assets and Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Acquired Intangible Assets and Liabilities	'	'	'
New intangible assets added	'	$2,900,000	'
New intangible liabilities added	'	200,000	'
Weighted average life of intangible assets	'	'4 years 4 months 24 days	'
Weighted average life of intangible liabilities	'	'6 months	'
Below-market lease contract value, gross	11,000,000	18,600,000	'
Accumulated amortization of below-market lease	4,400,000	10,100,000	'
Acquired Intangible Assets and Liabilities	'	'	'
Increase to rental income	800,000	1,500,000	1,700,000
Amortization of all other identified intangible assets	-823,000	-1,505,000	-1,650,000
Estimated amortization of acquired below-market leases, net of acquired above-market leases	'	'	'
2014	434,000	'	'
2015	548,000	'	'
2016	565,000	'	'
2017	596,000	'	'
2018	597,000	'	'
Thereafter	2,590,000	'	'
Total	5,330,000	'	'
Estimated amortization of all other identified intangible assets	'	'	'
2014	3,168,000	'	'
2015	2,071,000	'	'
2016	1,665,000	'	'
2017	1,172,000	'	'
2018	656,000	'	'
Thereafter	945,000	'	'
Total	9,677,000	'	'
Lease contracts value, gross	24,500,000	45,700,000	'
Accumulated amortization	14,800,000	28,600,000	'
Above-market leases	'	'	'
Estimated amortization of all other identified intangible assets	'	'	'
Lease contracts value, gross	4,100,000	6,800,000	'
Accumulated amortization	2,800,000	4,500,000	'
Other identified intangible assets	'	'	'
Acquired Intangible Assets and Liabilities	'	'	'
Amortization of all other identified intangible assets	$7,400,000	$18,100,000	$32,200,000

Investment_in_Real_Estate_Deta

Investment in Real Estate (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Investment in Real Estate	'	'
Land	$78,983	$85,868
Buildings and Improvements	717,007	596,405
Leasehold improvements	95,218	85,907
Construction in progress	157,317	61,328
Total investments in real estate	1,048,525	'
SV1, San Jose, CA	'	'
Investment in Real Estate	'	'
Land	6,863	'
Buildings and Improvements	119,525	'
Construction in progress	3,693	'
Total investments in real estate	130,081	'
SV2, Milpitas, CA	'	'
Investment in Real Estate	'	'
Land	5,086	'
Buildings and Improvements	24,202	'
Construction in progress	484	'
Total investments in real estate	29,772	'
SV3, Santa Clara, CA	'	'
Investment in Real Estate	'	'
Land	3,972	'
Buildings and Improvements	45,840	'
Construction in progress	130	'
Total investments in real estate	49,942	'
SV4, Santa Clara, CA	'	'
Investment in Real Estate	'	'
Land	4,442	'
Buildings and Improvements	86,226	'
Construction in progress	680	'
Total investments in real estate	91,348	'
SV5, Santa Clara, CA	'	'
Investment in Real Estate	'	'
Land	2,370	'
Buildings and Improvements	19,986	'
Total investments in real estate	22,356	'
Santa Clara Campus, Santa Clara, CA	'	'
Investment in Real Estate	'	'
Land	8,173	'
Buildings and Improvements	8,220	'
Construction in progress	9,384	'
Total investments in real estate	25,777	'
BO1, Somerville, MA	'	'
Investment in Real Estate	'	'
Land	6,100	'
Buildings and Improvements	77,919	'
Construction in progress	2,940	'
Total investments in real estate	86,959	'
NY1, New York, NY	'	'
Investment in Real Estate	'	'
Leasehold improvements	32,717	'
Construction in progress	46	'
Total investments in real estate	32,763	'
NY2, Secaucus, NJ	'	'
Investment in Real Estate	'	'
Land	386	'
Buildings and Improvements	14,031	'
Construction in progress	88,905	'
Total investments in real estate	103,322	'
VA1, Reston, VA	'	'
Investment in Real Estate	'	'
Land	6,903	'
Buildings and Improvements	106,171	'
Construction in progress	3,121	'
Total investments in real estate	116,195	'
VA2, Reston, VA	'	'
Investment in Real Estate	'	'
Construction in progress	34,030	'
Total investments in real estate	34,030	'
DC1, Washington, DC	'	'
Investment in Real Estate	'	'
Leasehold improvements	7,417	'
Construction in progress	269	'
Total investments in real estate	7,686	'
CH1, Chicago, IL	'	'
Investment in Real Estate	'	'
Land	5,493	'
Buildings and Improvements	82,011	'
Construction in progress	164	'
Total investments in real estate	87,668	'
LA1, Los Angeles, CA	'	'
Investment in Real Estate	'	'
Leasehold improvements	53,669	'
Construction in progress	2,938	'
Total investments in real estate	56,607	'
LA2, Los Angeles, CA	'	'
Investment in Real Estate	'	'
Land	28,467	'
Buildings and Improvements	122,912	'
Construction in progress	10,457	'
Total investments in real estate	161,836	'
MI1, Miami, FL	'	'
Investment in Real Estate	'	'
Land	728	'
Buildings and Improvements	9,964	'
Construction in progress	4	'
Total investments in real estate	10,696	'
DE1, Denver, CO	'	'
Investment in Real Estate	'	'
Leasehold improvements	730	'
Construction in progress	6	'
Total investments in real estate	736	'
DE2, Denver, CO	'	'
Investment in Real Estate	'	'
Leasehold improvements	685	'
Construction in progress	66	'
Total investments in real estate	$751	'

Other_Assets_Details

Other Assets (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Other Assets	'	'
Deferred leasing costs	$14,159	$12,444
Deferred rent receivable	17,265	15,017
Deferred financing costs	3,312	2,520
Corporate furniture, fixtures and equipment	7,346	4,152
Internal-use software	8,525	2,300
Other	5,195	6,149
Total	55,802	42,582
Estimated amortization of deferred leasing costs	'	'
2014	4,798	'
2015	3,843	'
2016	2,132	'
2017	1,155	'
2018	760	'
Thereafter	1,471	'
Total	$14,159	$12,444

Leases_Details

Leases (Details) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Future minimum lease payments to be received under noncancelable leases	'
2014	$129,832
2015	104,664
2016	77,789
2017	52,966
2018	35,051
Thereafter	71,141
Total	471,443
Operating leases	'
2014	19,028
2015	19,388
2016	19,076
2017	17,641
2018	15,975
Thereafter	64,918
Total	$156,026

Debt_Details

Debt (Details) (USD $)

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Jan. 31, 2014

Jun. 28, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Jan. 31, 2014

Feb. 03, 2014

Jan. 31, 2014

Feb. 03, 2014

Jan. 31, 2014

Jan. 31, 2014

Jan. 31, 2014

Jun. 28, 2013

Jan. 02, 2013

SV1 - Mortgage loan

SV1 - Mortgage loan

SV1 - Mortgage loan

Revolving credit facility

Revolving credit facility

Revolving credit facility

Revolving credit facility

Revolving credit facility

Revolving credit facility

Revolving credit facility

Revolving credit facility

Revolving credit facility

Revolving credit facility

Revolving credit facility

Revolving credit facility

Senior Unsecured Term Loan

Senior Unsecured Term Loan

Senior Unsecured Term Loan

Senior Unsecured Term Loan

Senior Unsecured Term Loan

Senior Unsecured Term Loan

Senior Unsecured Term Loan

Prior facility

Prior facility

Subsequent event

item

Operating partnership

Minimum

Maximum

LIBOR

LIBOR

LIBOR

Base rate

Base rate

Base rate

Subsequent event

Subsequent event

Subsequent event

Subsequent event

Subsequent event

Subsequent event

Subsequent event

Operating partnership

Minimum

Maximum

Operating partnership

Minimum

Maximum

Interest rate swap

Operating partnership

LIBOR

LIBOR

LIBOR

LIBOR

Operating partnership

Operating partnership

Operating partnership

Operating partnership

Interest rate swap

Operating partnership

Minimum

Maximum

Operating partnership

Operating partnership

Debt

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest rate as of reporting date (as a percent)

'

'

3.67%

3.71%

'

'

2.17%

2.46%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total principal outstanding

$232,500,000

$59,750,000

$58,250,000

$59,750,000

'

'

$174,250,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Commitment under the credit agreement

'

'

'

'

'

355,000,000

405,000,000

'

500,000,000

'

'

'

'

'

'

'

'

100,000,000

'

200,000,000

'

'

'

'

355,000,000

225,000,000

Term of loan facility

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'5 years

'

'

'

'

'

'

'

'

Number of options available for extensions

'

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Extension fee (as a percent)

'

'

'

'

'

'

0.25%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total increase in commitment under accordion feature

'

'

'

'

'

50,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

100,000,000

'

'

'

'

'

'

Reference rate

'

'

'

'

'

'

'

'

'

'

'

'LIBOR

'

'

'base rate

'

'

'

'

'

'one month LIBOR

'LIBOR

'

'

'

'

Interest rate margin (as a percent)

'

'

'

'

'

'

'

'

'

'

'

'

2.00%

2.75%

'

1.00%

1.75%

'

3.23%

'

'

'

1.75%

2.65%

'

'

Notional amount of interest rate derivatives

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100,000,000

'

'

'

'

'

'

'

Amount borrowed under term loan or revolving credit facility

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100,000,000

'

'

'

'

'

'

'

Term of derivative

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'5 years

'

'

'

'

'

'

'

Repayment of loan facility

'

'

'

'

58,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount available for borrowing under the facility

'

'

'

'

'

'

222,400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Outstanding borrowings

'

'

'

'

'

'

$174,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Leverage ratio, Covenant (as a percent)

'

'

'

'

'

'

'

'

'

'

60.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Leverage ratio (as a percent)

'

'

'

'

'

'

15.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Secured debt ratio, Covenant (as a percent)

'

'

'

'

'

'

'

'

'

'

4.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Secured debt ratio (as a percent)

'

'

'

'

'

'

3.70%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fixed charge coverage ratio, Covenant

'

'

'

'

'

'

'

'

'

1.75

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fixed charge coverage ratio

'

'

'

'

'

'

'

'

'

7.20%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unhedged variable rate debt ratio, Covenant (as a percent)

'

'

'

'

'

'

'

'

'

'

30.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unhedged variable rate debt ratio (as a percent)

'

'

'

'

'

'

14.90%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt_Details_2

Debt (Details 2) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Debt maturities	'
2017	$132,500
Thereafter	100,000
Total	$232,500

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)	0 Months Ended	12 Months Ended
	Nov. 15, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stockholders' Equity	'	'	'	'
Stock authorized to be issued (in shares)	'	120,000,000	'	'
Common stock authorized to be issued (in shares)	'	100,000,000	100,000,000	'
Preferred stock authorized to be issued (in shares)	'	20,000,000	'	'
Common stock, shares issued	'	21,387,152	21,202,673	'
Common stock, shares outstanding	'	21,387,152	21,202,673	'
Proceeds from exercise of stock options	'	$925,000	$1,564,000	$31,000
Common Operating Partnership units redeemed for common stock (in shares)	889,610	'	'	'
Reduction to noncontrolling interests in the Operating Partnership and an increase to common stock and additional paid in capital	13,800,000	'	'	'
Number of shares issued	'	4,600,000	4,600,000	'
Dividend rate on preferred stock (as a percent)	'	7.25%	7.25%	'
Net Proceeds from issuance of preferred stock	'	'	110,615,000	'
Liquidation preference on preferred stock (in dollars per share)	'	$25	$25	'
2010 Plan	'	'	'	'
Stockholders' Equity	'	'	'	'
Proceeds from exercise of stock options	'	900,000	1,600,000	'
Amount of shares of common stock issued under the plan	'	184,479	454,879	214,142
2010 Plan | Maximum	'	'	'	'
Stockholders' Equity	'	'	'	'
Proceeds from exercise of stock options	'	'	'	100,000
Series A Cumulative Redeemable Preferred Stock	'	'	'	'
Stockholders' Equity	'	'	'	'
Number of shares issued	'	'	4,600,000	'
Dividend rate on preferred stock (as a percent)	'	'	7.25%	'
Net Proceeds from issuance of preferred stock	'	'	$110,600,000	'
Cumulative dividends each year on preferred stock (in dollars per share)	'	$1.81	'	'
Liquidation preference on preferred stock (in dollars per share)	'	$25	'	'
Redemption price of preferred stock (in dollars per share)	'	$25	'	'
Minimum number of quarters in which no payment of preferred stock dividends leads to entitlement of voting rights	'	6	'	'
Conversion ratio of preferred stock	'	1.944	'	'

Stockholders_Equity_Details_2

Stockholders' Equity (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	Jan. 31, 2013	Dec. 31, 2012	Jan. 31, 2012	Dec. 31, 2011	Jan. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2014
	Minimum	Common Stock	Common Stock	Common Stock	Common Stock	Common Stock	Common Stock	Preferred stock	Preferred stock	Preferred stock	Preferred stock
							Subsequent event				Subsequent event
Dividends	'	'	'	'	'	'	'	'	'	'	'
Ordinary income (in dollars per share)	'	$1.16	'	$0.81	'	$0.57	'	$1.98	'	'	'
Total dividend (in dollars per share)	'	$1.16	'	$0.81	'	$0.57	'	$1.98	$0	$0	'
Ordinary dividend paid (in dollars per share)	'	'	$0.27	'	$0.18	'	$0.35	'	'	'	$0.45
Common stock distributions as percentage of REIT taxable income	90.00%	'	'	'	'	'	'	'	'	'	'
Common stock distributions as percentage of net income (after tax), from foreclosure property	90.00%	'	'	'	'	'	'	'	'	'	'

Noncontrolling_Interests_Opera2

Noncontrolling Interests - Operating Partnership (Details) (USD $)	0 Months Ended	3 Months Ended			12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 12, 2012	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Noncontrolling Interests - Operating Partnership	'	'	'	'	'	'
Conversion ratio for common operating partnership units	'	'	'	'	1	'
Noncontrolling Interests Operating Partnership	'	'	'	'	'	'
Number of Units (in shares)	'	'	'	'	46,257,532	45,964,232
Percentage of Total	'	'	'	'	100.00%	100.00%
Shares of common stock issued related to employee compensation arrangements	'	'	'	'	286,964	'
Common Operating Partnership units issued to employees upon their vesting in the incentive unit awards (in shares)	'	'	'	'	7,138	'
Quarterly distributions received by holders of operating partnership units (in dollars per unit)	'	$0.27	$0.27	$0.27	$0.35	'
Preferred Operating Partnership units issued to CoreSite Realty Corporation (in shares)	4,600,000	'	'	'	'	'
Redemption value of the noncontrolling interests	'	'	'	'	$816.40	'
Closing price of the Company's stock (in dollars per share)	'	'	'	'	$32.19	'
The Company	'	'	'	'	'	'
Noncontrolling Interests Operating Partnership	'	'	'	'	'	'
Number of Units (in shares)	'	'	'	'	20,896,685	20,610,523
Percentage of Total	'	'	'	'	45.20%	44.80%
Common units held by third parties	'	'	'	'	'	'
Noncontrolling Interests Operating Partnership	'	'	'	'	'	'
Number of Units (in shares)	'	'	'	'	25,275,390	25,275,390
Percentage of Total	'	'	'	'	54.60%	55.00%
Incentive units held by employees	'	'	'	'	'	'
Noncontrolling Interests Operating Partnership	'	'	'	'	'	'
Number of Units (in shares)	'	'	'	'	85,457	78,319
Percentage of Total	'	'	'	'	0.20%	0.20%

Equity_Incentive_Plan_Details

Equity Incentive Plan (Details) (USD $)

0 Months Ended

12 Months Ended

In Millions, except Share data, unless otherwise specified

22-May-13

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

2010 Plan

2010 Plan

Stock options

Stock options

Stock options

Stock options

Stock options

Restricted Awards

Restricted Awards

Restricted Awards

Restricted Awards

Restricted awards

Restricted awards

Restricted awards

RSUs

RSUs

RSUs

Common Operating Partnership Units

Maximum

Weighted average

Equity Incentive Plan

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Increase in number of shares of common stock authorized for issuance

3,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Shares of common stock that were available for issuance pursuant to the 2010 Plan

6,000,000

3,686,242

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Shares Subject to Option

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Options outstanding at the beginning of the period (in shares)

'

'

1,017,195

998,051

587,555

'

'

'

'

'

'

'

'

'

'

'

'

'

Granted (in shares)

'

'

209,268

236,893

543,380

'

'

'

'

'

'

'

'

'

'

'

'

'

Forfeited (in shares)

'

'

-37,232

-119,723

-122,848

'

'

'

'

'

'

'

'

'

'

'

'

'

Expired (in shares)

'

'

-535

-156

-8,074

'

'

'

'

'

'

'

'

'

'

'

'

'

Exercised (in shares)

'

'

-54,781

-97,870

-1,962

'

'

'

'

'

'

'

'

'

'

'

'

'

Options outstanding at the end of the period (in shares)

'

'

1,133,915

1,017,195

998,051

587,555

'

'

'

'

'

'

'

'

'

'

'

'

Exercisable at the end of the period (in shares)

'

'

498,176

287,036

130,942

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted Average Exercise Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Options outstanding at the beginning of the period (in dollars per share)

'

'

$17.25

$15.63

$16

'

'

'

'

'

'

'

'

'

'

'

'

'

Granted (in dollars per share)

'

'

$32.50

$23.87

$15.27

'

'

'

'

'

'

'

'

'

'

'

'

'

Forfeited (in dollars per share)

'

'

$23

$16.62

$15.80

'

'

'

'

'

'

'

'

'

'

'

'

'

Expired (in dollars per share)

'

'

$34.82

$16

$16

'

'

'

'

'

'

'

'

'

'

'

'

'

Exercised (in dollars per share)

'

'

$16.86

$16.04

$16

'

'

'

'

'

'

'

'

'

'

'

'

'

Options outstanding at the end of the period (in dollars per share)

'

'

$19.89

$17.25

$15.63

$16

'

'

'

'

'

'

'

'

'

'

'

'

Exercisable at the end of the period (in dollars per share)

'

'

$16.51

$15.74

$16

'

'

'

'

'

'

'

'

'

'

'

'

'

Weighted Average Remaining Contractual Term

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Options outstanding at the end of the period

'

'

'7 years 7 months 6 days

'8 years 2 months 12 days

'8 years 10 months 24 days

'9 years 8 months 12 days

'

'

'

'

'

'

'

'

'

'

'

'

Exercisable at the end of the period

'

'

'7 years 1 month 6 days

'7 years 10 months 24 days

'8 years 8 months 12 days

'

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate Intrinsic Value

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Exercised

'

'

$0.10

$0.80

'

'

$0.10

'

'

'

'

'

'

'

'

'

'

'

Outstanding at the end of the period

'

'

14

10.6

2.2

'

'

'

'

'

'

'

'

'

'

'

'

'

Exercisable at the end of the period

'

'

7.8

3.4

0.2

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Shares Subject to Option

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested balance at the beginning of the period (in shares)

'

'

730,159

867,109

587,555

'

'

'

'

'

'

'

'

'

'

'

'

'

Granted (in shares)

'

'

209,268

236,893

543,380

'

'

'

'

'

'

'

'

'

'

'

'

'

Forfeited (in shares)

'

'

-37,232

-119,723

-122,848

'

'

'

'

'

'

'

'

'

'

'

'

'

Vested (in shares)

'

'

-266,456

-254,120

-140,978

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested balance at the end of the period (in shares)

'

'

635,739

730,159

867,109

587,555

'

'

'

'

'

'

'

'

'

'

'

'

Weighted Average Fair Value at Grant

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested balance at the beginning of the period (in dollars per share)

'

'

$5.70

$4.92

$4.95

'

'

'

'

'

'

'

'

'

'

'

'

'

Granted (in dollars per share)

'

'

$10.01

$7.76

$4.89

'

'

'

'

'

'

'

'

'

'

'

'

'

Forfeited (in dollars per share)

'

'

$7.21

$5.24

$4.93

'

'

'

'

'

'

'

'

'

'

'

'

'

Vested (in dollars per share)

'

'

$5.54

$4.96

$4.92

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested balance at the end of the period (in dollars per share)

'

'

$7.10

$5.70

$4.92

$4.95

'

'

'

'

'

'

'

'

'

'

'

'

Assumptions used to value the stock options granted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected term

'

'

'6 years 3 months

'6 years 3 months

'6 years 3 months

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected volatility (as a percent)

'

'

43.86%

44.08%

43.07%

'

'

'

'

'

'

'

'

'

'

'

'

'

Expected annual dividend (as a percent)

'

'

3.33%

3.00%

3.41%

'

'

'

'

'

'

'

'

'

'

'

'

'

Risk-free rate (as a percent)

'

'

1.26%

1.56%

2.76%

'

'

'

'

'

'

'

'

'

'

'

'

'

Restricted Awards

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Grant date value

'

'

'

'

'

'

'

'

'

'

'

6.1

9.9

4

0.2

0.2

0.2

'

Unvested balance at the beginning of the period (in shares)

'

'

'

'

'

'

'

598,695

343,231

195,437

'

'

'

'

'

'

'

'

Granted (in shares)

'

'

'

'

'

'

'

194,302

412,780

273,473

'

188,710

405,608

263,393

5,592

7,172

10,080

25,883

Forfeited (in shares)

'

'

'

'

'

'

'

-58,199

-48,599

-51,213

'

'

'

'

'

'

'

-1,491

Vested (in shares)

'

'

'

'

'

'

'

-239,647

-108,717

-74,466

'

'

'

'

'

'

'

'

Unvested balance at the end of the period (in shares)

'

'

'

'

'

'

'

495,151

598,695

343,231

'

'

'

'

'

'

'

0

Weighted Average Fair Value at Grant Date

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested balance at the beginning of the period (in dollars per share)

'

'

'

'

'

'

'

$21.37

$15.35

$15.98

'

'

'

'

'

'

'

'

Granted (in dollars per share)

'

'

'

'

'

'

'

$32.43

$24.59

$15.19

'

'

'

'

'

'

'

$15.98

Forfeited (in dollars per share)

'

'

'

'

'

'

'

$28.44

$18.26

$15.81

'

'

'

'

'

'

'

'

Vested (in dollars per share)

'

'

'

'

'

'

'

$20.96

$15.46

$16.10

'

'

'

'

'

'

'

'

Unvested balance at the end of the period (in dollars per share)

'

'

'

'

'

'

'

$25.08

$21.37

$15.35

'

'

'

'

'

'

'

'

Total grant date fair value of operating partnership units

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

0.4

Compensation cost not yet recognized

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unearned compensation

'

'

3.3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unearned compensation

'

'

'

'

'

'

'

$9

'

'

'

'

'

'

'

'

'

'

Vesting period

'

'

'2 years

'

'

'

'

'

'

'

'2 years 1 month 6 days

'

'

'

'

'

'

'

Vested shares outstanding

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

24,392

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share	'	'	'	'	'	'	'	'	'	'	'
Net income (loss) attributable to common shares	$3,135	$2,901	$2,618	$1,849	$1,862	$1,320	$826	$600	$10,503	$4,608	($4,611)
Weighted average common shares outstanding - basic	'	'	'	'	'	'	'	'	20,826,622	20,537,946	19,609,375
Effect of potentially dilutive common shares:	'	'	'	'	'	'	'	'	'	'	'
Stock options	'	'	'	'	'	'	'	'	383,743	211,222	'
Unvested restricted awards	'	'	'	'	'	'	'	'	292,847	243,122	'
Weighted average common shares outstanding - diluted	'	'	'	'	'	'	'	'	21,503,212	20,992,290	19,609,375
Net income (loss) per share attributable to common shares	'	'	'	'	'	'	'	'	'	'	'
Basic (in dollars per share)	$0.15	$0.14	$0.13	$0.08	$0.09	$0.06	$0.04	$0.03	$0.50	$0.22	($0.24)
Diluted (in dollars per share)	$0.15	$0.14	$0.12	$0.08	$0.09	$0.06	$0.04	$0.03	$0.49	$0.22	($0.24)
Potentially dilutive securities excluded in calculation of basic and diluted income (loss) per share	'	'	'	'	'	'	'	'	169,875	153,972	1,341,282

Estimated_Fair_Value_of_Financ1

Estimated Fair Value of Financial Instruments (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Fair value of assets and liabilities measured on a recurring basis	'	'
Balance of mortgage loan payable and revolving credit facility	$58,250	$59,750
Significant Unobservable Inputs (Level 3)	'	'
Fair value of assets and liabilities measured on a recurring basis	'	'
Balance of mortgage loan payable and revolving credit facility	$232,500	$59,800

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Related Party Transactions	'	'	'
Rental revenue	$131,080	$116,146	$101,449
Affiliate of the Carlyle Group | VA1- Mortgage loan	'	'	'
Related Party Transactions	'	'	'
Net rentable space leased to an affiliate (in square feet)	1,520	'	'
Common interest (as a percent)	54.60%	'	'
Rental revenue	$400	$300	$200
Affiliate of the Carlyle Group | LA1, Los Angeles, CA	'	'	'
Related Party Transactions	'	'	'
Net rentable space leased to an affiliate (in square feet)	375	'	'

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	12 Months Ended		0 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2013	Jan. 24, 2014
		Former owner of acquired entity	Mr. Appleby
		Comfluent
Other expenses	'	'	'
Open commitments related to construction contracts	$28.90	'	'
Open commitments related to telecommunications contracts	5.6	'	'
Term of Completion of IPO for Calculating Tax Protection Provisions Expiration Period	'7 years	'	'
Percentage of Operating Partnership Units that are Disposed in Certain Taxable Transactions	90.00%	'	'
Commitments and Contingencies	'	'	'
Estimated compensation amount	'	8	'
Accrued leasing commission	1.2	'	'
Estimated expense as per the employment agreement during the first quarter of 2014	'	'	$0.90

Quarterly_Financial_Informatio2

Quarterly Financial Information (unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information (unaudited)	'	'	'	'	'	'	'	'	'	'	'
Revenue	$61,440	$60,635	$57,667	$55,091	$55,252	$53,762	$50,636	$47,284	$234,833	$206,934	$172,846
Operating income	9,740	9,259	8,866	6,805	5,936	5,059	3,814	2,234	34,670	17,043	-7,090
Net income	9,029	8,509	7,879	6,195	4,578	2,947	1,848	1,343	31,612	10,716	-10,779
Net income attributable to common shares	$3,135	$2,901	$2,618	$1,849	$1,862	$1,320	$826	$600	$10,503	$4,608	($4,611)
Net income per share attributable to common shares - basic (in dollars per share)	$0.15	$0.14	$0.13	$0.08	$0.09	$0.06	$0.04	$0.03	$0.50	$0.22	($0.24)
Net income per share attributable to common shares - diluted (in dollars per share)	$0.15	$0.14	$0.12	$0.08	$0.09	$0.06	$0.04	$0.03	$0.49	$0.22	($0.24)

Schedule_III_Real_Estate_and_A1

Schedule III Real Estate and Accumulated Depreciation (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Real Estate and Accumulated Depreciation	'	'	'	'
Encumbrances	$58,250,000	'	'	'
Initial Cost	'	'	'	'
Land	89,689,000	'	'	'
Building and Improvements	390,196,000	'	'	'
Costs Capitalized Subsequent to Acquisition	568,640,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	78,983,000	'	'	'
Building and Improvements	969,542,000	'	'	'
Total	1,048,525,000	829,508,000	741,981,000	624,122,000
Accumulated Depreciation	155,704,000	105,433,000	64,428,000	32,943,000
Aggregate cost of the total properties for federal income tax purposes	947,300,000	'	'	'
SV1, San Jose, CA	'	'	'	'
Real Estate and Accumulated Depreciation	'	'	'	'
Encumbrances	58,250,000	'	'	'
Initial Cost	'	'	'	'
Land	6,863,000	'	'	'
Building and Improvements	91,719,000	'	'	'
Costs Capitalized Subsequent to Acquisition	31,499,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	6,863,000	'	'	'
Building and Improvements	123,218,000	'	'	'
Total	130,081,000	'	'	'
Accumulated Depreciation	11,787,000	'	'	'
SV2, Milpitas, CA	'	'	'	'
Initial Cost	'	'	'	'
Land	5,086,000	'	'	'
Building and Improvements	5,046,000	'	'	'
Costs Capitalized Subsequent to Acquisition	19,640,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	5,086,000	'	'	'
Building and Improvements	24,686,000	'	'	'
Total	29,772,000	'	'	'
Accumulated Depreciation	10,454,000	'	'	'
SV3, Santa Clara, CA	'	'	'	'
Initial Cost	'	'	'	'
Land	3,972,000	'	'	'
Building and Improvements	3,482,000	'	'	'
Costs Capitalized Subsequent to Acquisition	42,488,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	3,972,000	'	'	'
Building and Improvements	45,970,000	'	'	'
Total	49,942,000	'	'	'
Accumulated Depreciation	15,972,000	'	'	'
SV4, Santa Clara, CA	'	'	'	'
Initial Cost	'	'	'	'
Land	4,442,000	'	'	'
Building and Improvements	3,716,000	'	'	'
Costs Capitalized Subsequent to Acquisition	83,190,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	4,442,000	'	'	'
Building and Improvements	86,906,000	'	'	'
Total	91,348,000	'	'	'
Accumulated Depreciation	9,079,000	'	'	'
SV5, Santa Clara, CA	'	'	'	'
Initial Cost	'	'	'	'
Land	2,370,000	'	'	'
Costs Capitalized Subsequent to Acquisition	19,986,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	2,370,000	'	'	'
Building and Improvements	19,986,000	'	'	'
Total	22,356,000	'	'	'
Accumulated Depreciation	80,000	'	'	'
Clara Campus, Santa Clara, CA	'	'	'	'
Initial Cost	'	'	'	'
Land	9,116,000	'	'	'
Building and Improvements	9,240,000	'	'	'
Costs Capitalized Subsequent to Acquisition	7,421,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	8,173,000	'	'	'
Building and Improvements	17,604,000	'	'	'
Total	25,777,000	'	'	'
Accumulated Depreciation	1,917,000	'	'	'
BO1, Somerville, MA	'	'	'	'
Initial Cost	'	'	'	'
Land	6,100,000	'	'	'
Building and Improvements	26,748,000	'	'	'
Costs Capitalized Subsequent to Acquisition	54,111,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	6,100,000	'	'	'
Building and Improvements	80,859,000	'	'	'
Total	86,959,000	'	'	'
Accumulated Depreciation	24,257,000	'	'	'
NY1, New York, NY	'	'	'	'
Initial Cost	'	'	'	'
Costs Capitalized Subsequent to Acquisition	32,763,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Building and Improvements	32,763,000	'	'	'
Total	32,763,000	'	'	'
Accumulated Depreciation	11,241,000	'	'	'
NY2, Secaucus, NJ	'	'	'	'
Initial Cost	'	'	'	'
Land	4,952,000	'	'	'
Building and Improvements	18,408,000	'	'	'
Costs Capitalized Subsequent to Acquisition	79,962,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	386,000	'	'	'
Building and Improvements	102,936,000	'	'	'
Total	103,322,000	'	'	'
Accumulated Depreciation	80,000	'	'	'
VA1, Reston, VA	'	'	'	'
Initial Cost	'	'	'	'
Land	6,903,000	'	'	'
Building and Improvements	32,939,000	'	'	'
Costs Capitalized Subsequent to Acquisition	76,353,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	6,903,000	'	'	'
Building and Improvements	109,292,000	'	'	'
Total	116,195,000	'	'	'
Accumulated Depreciation	26,007,000	'	'	'
VA2, Reston, VA	'	'	'	'
Initial Cost	'	'	'	'
Land	5,197,000	'	'	'
Costs Capitalized Subsequent to Acquisition	28,833,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Building and Improvements	34,030,000	'	'	'
Total	34,030,000	'	'	'
DC1, Washington, DC	'	'	'	'
Initial Cost	'	'	'	'
Building and Improvements	4,797,000	'	'	'
Costs Capitalized Subsequent to Acquisition	2,889,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Building and Improvements	7,686,000	'	'	'
Total	7,686,000	'	'	'
Accumulated Depreciation	2,124,000	'	'	'
CH1, Chicago, IL	'	'	'	'
Initial Cost	'	'	'	'
Land	5,493,000	'	'	'
Building and Improvements	49,522,000	'	'	'
Costs Capitalized Subsequent to Acquisition	32,653,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	5,493,000	'	'	'
Building and Improvements	82,175,000	'	'	'
Total	87,668,000	'	'	'
Accumulated Depreciation	10,727,000	'	'	'
LA1, Los Angeles, CA	'	'	'	'
Initial Cost	'	'	'	'
Building and Improvements	41,099,000	'	'	'
Costs Capitalized Subsequent to Acquisition	15,508,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Building and Improvements	56,607,000	'	'	'
Total	56,607,000	'	'	'
Accumulated Depreciation	13,681,000	'	'	'
LA2, Los Angeles, CA	'	'	'	'
Initial Cost	'	'	'	'
Land	28,467,000	'	'	'
Building and Improvements	94,114,000	'	'	'
Costs Capitalized Subsequent to Acquisition	39,255,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	28,467,000	'	'	'
Building and Improvements	133,369,000	'	'	'
Total	161,836,000	'	'	'
Accumulated Depreciation	16,516,000	'	'	'
MI1, Miami, FL	'	'	'	'
Initial Cost	'	'	'	'
Land	728,000	'	'	'
Building and Improvements	9,325,000	'	'	'
Costs Capitalized Subsequent to Acquisition	643,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Land	728,000	'	'	'
Building and Improvements	9,968,000	'	'	'
Total	10,696,000	'	'	'
Accumulated Depreciation	1,440,000	'	'	'
DE1, Denver, CO	'	'	'	'
Initial Cost	'	'	'	'
Building and Improvements	37,000	'	'	'
Costs Capitalized Subsequent to Acquisition	699,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Building and Improvements	736,000	'	'	'
Total	736,000	'	'	'
Accumulated Depreciation	164,000	'	'	'
DE2, Denver, CO	'	'	'	'
Initial Cost	'	'	'	'
Building and Improvements	4,000	'	'	'
Costs Capitalized Subsequent to Acquisition	747,000	'	'	'
Gross Amount Carried As of Year End	'	'	'	'
Building and Improvements	751,000	'	'	'
Total	751,000	'	'	'
Accumulated Depreciation	$178,000	'	'	'

Schedule_III_Real_Estate_and_A2

Schedule III Real Estate and Accumulated Depreciation (Details 2) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property	'	'	'
Balance, beginning of period	$829,508	$741,981	$624,122
Additions - property acquisitions	23,360	'	'
Additions - improvements	195,657	87,527	117,859
Balance, end of period	1,048,525	829,508	741,981
Accumulated Depreciation	'	'	'
Balance, beginning of period	105,433	64,428	32,943
Additions - depreciation, net of disposals	50,271	41,005	31,485
Balance, end of period	$155,704	$105,433	$64,428