CoreSite Realty 10-K 10 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Feb. 08, 2017	Jun. 30, 2016
Document and Entity Information
Entity Registrant Name	CoreSite Realty Corp
Entity Central Index Key	1,490,892
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 2,493.3
Entity Common Stock, Shares Outstanding		33,895,316
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investments in real estate:
Land	$ 100,258	$ 74,819
Buildings and improvements	1,472,580	1,037,127
Total investments in real estate	1,572,838	1,111,946
Less: Accumulated depreciation and amortization	(369,303)	(284,219)
Net investment in operating properties	1,203,535	827,727
Construction in progress	70,738	183,189
Net investments in real estate	1,274,273	1,010,916
Cash and cash equivalents	4,429	6,854
Accounts and other receivables, net of allowance for doubtful accounts of $209 and $56 as of December 31, 2016, and December 31, 2015, respectively	25,125	12,235
Lease intangibles, net of accumulated amortization of $12,385 and $11,437 as of December 31, 2016, and December 31, 2015, respectively	9,913	4,714
Goodwill	41,191	41,191
Other assets, net	96,372	86,633
Total assets	1,451,303	1,162,543
Liabilities:
Debt, net of unamortized deferred financing costs of $3,550 and $1,243 as of December 31, 2016, and December 31, 2015, respectively	690,450	391,007
Accounts payable and accrued expenses	72,519	75,783
Accrued dividends and distributions	41,849	28,104
Deferred rent payable	7,694	7,934
Acquired below-market lease contracts, net of accumulated amortization of $5,439 and $5,279 as of December 31, 2016, and December 31, 2015, respectively	4,292	4,693
Unearned revenue, prepaid rent and other liabilities	37,413	28,717
Total liabilities	854,217	536,238
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, 2016, and December 31, 2015	115,000	115,000
Common Stock, par value $0.01, 100,000,000 shares authorized and 33,896,771 and 30,650,703 shares issued and outstanding at December 31, 2016, and December 31, 2015, respectively	334	301
Additional paid-in capital	438,531	390,200
Accumulated other comprehensive loss	(101)	(493)
Distributions in excess of net income	(118,038)	(88,891)
Total stockholders' equity	435,726	416,117
Noncontrolling interests	161,360	210,188
Total equity	597,086	626,305
Total liabilities and equity	$ 1,451,303	$ 1,162,543

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
CONDENSED CONSOLIDATED BALANCE SHEETS
Allowance for doubtful accounts (in dollars)	$ 209,000	$ 56,000
Accumulated amortization, lease intangibles (in dollars)	12,385,000	11,437,000
Unamortized Debt Issuance Expense	3,550,000	1,243,000
Accumulated amortization, acquired below-market lease contracts (in dollars)	$ 5,439,000	$ 5,279,000
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	33,896,771	30,650,703
Common Stock, shares outstanding	33,896,771	30,650,703

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Data center revenue:
Rental revenue	$ 218,060	$ 183,300	$ 149,294
Power revenue	111,541	89,495	71,227
Interconnection revenue	53,077	44,234	35,355
Tenant reimbursement and other	9,086	8,295	8,702
Office, light-industrial and other revenue	8,588	7,968	7,842
Total operating revenues	400,352	333,292	272,420
Operating expenses:
Property operating and maintenance	107,212	89,805	75,119
Real estate taxes and insurance	14,250	12,144	7,578
Depreciation and amortization	108,652	95,702	80,722
Sales and marketing	17,495	15,930	14,554
General and administrative	35,369	34,179	27,842
Rent	22,631	21,075	20,397
Impairment of internal-use software		322	1,959
Transaction Costs	126	51	62
Total operating expenses	305,735	269,208	228,233
Operating income	94,617	64,084	44,187
Gain (loss) on real estate disposal		36	1,208
Interest income	35	6	6
Interest expense	(12,612)	(7,104)	(5,311)
Income before income taxes	82,040	57,022	40,090
Income tax expense	(119)	(163)	(38)
Net income	81,921	56,859	40,052
Net income attributable to noncontrolling interests	23,212	22,153	17,287
Net income attributable to CoreSite Realty Corporation	58,709	34,706	22,765
Preferred stock dividends	(8,338)	(8,338)	(8,338)
Net income attributable to common shares	$ 50,371	$ 26,368	$ 14,427
Net income per share attributable to common shares:
Basic (in dollars per share)	$ 1.56	$ 1.05	$ 0.68
Diluted (in dollars per share)	$ 1.54	$ 1.03	$ 0.66
Weighted average common shares outstanding
Basic (in shares)	32,289,414	25,218,500	21,161,614
Diluted (in shares)	32,732,059	25,706,568	21,740,707

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 81,921	$ 56,859	$ 40,052
Other comprehensive income (loss):
Unrealized gain (loss) on derivative contracts	(1,112)	(2,426)	(1,409)
Reclassification of other comprehensive income to interest expense	1,740	1,930	1,134
Comprehensive income	82,549	56,363	39,777
Comprehensive income attributable to noncontrolling interests	23,242	21,724	17,137
Comprehensive income attributable to CoreSite Realty Corporation	$ 59,307	$ 34,639	$ 22,640

CONSOLIDATED STATEMENTS OF EQUI

CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Distributions in Excess of Net Income	Total Stockholders' Equity	Noncontrolling Interests	Total
Balance at Dec. 31, 2013	$ 115,000	$ 209	$ 267,465		$ (50,264)	$ 332,410	$ 355,897	$ 688,307
Balance (in shares) at Dec. 31, 2013		21,387,152
Increase (Decrease) in Stockholders' Equity
Issuance of stock awards, net of forfeitures (in shares)		181,124
Exercise of stock options, net of settlements		$ 1	944			945		945
Exercise of stock options, net of settlements (in shares)		189,090
Share-based compensation		$ 2	6,629			6,631		6,631
Dividends declared on preferred stock					(8,338)	(8,338)		(8,338)
Dividends and distributions					(31,701)	(31,701)	(37,280)	(68,981)
Net income					22,765	22,765	17,287	40,052
Other comprehensive income (loss)				$ (125)		(125)	(150)	(275)
Balance at Dec. 31, 2014	115,000	$ 212	275,038	(125)	(67,538)	322,587	335,754	658,341
Balance (in shares) at Dec. 31, 2014		21,757,366
Increase (Decrease) in Stockholders' Equity
Redemption of noncontrolling interests		$ 85	110,396	(301)		110,180	(110,180)
Redemption of noncontrolling interests (in shares)		8,500,000
Issuance of stock awards, net of forfeitures (in shares)		207,937
Exercise of stock options, net of settlements		$ 3	(2,866)			(2,863)		(2,863)
Exercise of stock options, net of settlements (in shares)		185,400
Share-based compensation		$ 1	7,632			7,633		7,633
Dividends declared on preferred stock					(8,338)	(8,338)		(8,338)
Dividends and distributions					(47,721)	(47,721)	(37,110)	(84,831)
Net income					34,706	34,706	22,153	56,859
Other comprehensive income (loss)				(67)		(67)	(429)	(496)
Balance at Dec. 31, 2015	115,000	$ 301	390,200	(493)	(88,891)	416,117	210,188	626,305
Balance (in shares) at Dec. 31, 2015		30,650,703
Increase (Decrease) in Stockholders' Equity
Redemption of noncontrolling interests		$ 30	37,550	(206)		37,374	(37,374)
Redemption of noncontrolling interests (in shares)		3,007,000
Issuance of stock awards, net of forfeitures (in shares)		164,408
Exercise of stock options, net of settlements		$ 1	1,289			1,290		1,290
Exercise of stock options, net of settlements (in shares)		74,660
Share-based compensation		$ 2	9,492			9,494		9,494
Dividends declared on preferred stock					(8,338)	(8,338)		(8,338)
Dividends and distributions					(79,518)	(79,518)	(34,696)	(114,214)
Net income					58,709	58,709	23,212	81,921
Other comprehensive income (loss)				598		598	30	628
Balance at Dec. 31, 2016	$ 115,000	$ 334	$ 438,531	$ (101)	$ (118,038)	$ 435,726	$ 161,360	$ 597,086
Balance (in shares) at Dec. 31, 2016		33,896,771

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 81,921	$ 56,859	$ 40,052
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	108,652	95,702	80,722
Amortization of above/below market leases	(541)	(520)	(556)
Amortization of deferred financing costs	1,333	1,246	1,897
Gain on real estate disposal		(36)	(1,208)
Share-based compensation	8,892	7,114	6,125
Bad debt expense	398	201	648
Changes in operating assets and liabilities:
Accounts receivable	(13,199)	(2,146)	(599)
Deferred rent receivable	(7,083)	(7,799)	(4,245)
Deferred leasing costs	(14,395)	(17,555)	(21,390)
Other assets	(8,819)	(5,535)	(4,459)
Accounts payable and accrued expenses	4,910	6,532	(4,160)
Unearned revenue, prepaid rent and other liabilities	8,696	9,561	7,350
Deferred rent payable	(240)	(1,051)	(661)
Net cash provided by operating activities	170,525	142,573	99,516
CASH FLOWS FROM INVESTING ACTIVITIES
Tenant improvements	(5,878)	(7,736)	(5,893)
Real estate improvements	(293,359)	(122,196)	(100,299)
Acquisition of Reston Campus Expansion	(64,965)
Proceeds from real estate disposal		2,399
Net cash used in investing activities	(364,202)	(127,533)	(106,192)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from exercise of stock options	1,290	1,393	2,354
Offering costs			(147)
Proceeds from revolving credit facility	299,500	87,000	88,250
Payments on revolving credit facility	(247,750)	(163,250)	(44,000)
Proceeds from unsecured term loan	250,000	150,000	100,000
Repayments of mortgage loans payable			(58,250)
Payments of loan fees and costs	(2,981)	(2,315)	(1,000)
Payments to net settle equity awards		(4,256)	(1,410)
Dividends and distributions	(108,807)	(87,420)	(73,772)
Net cash provided by (used in) financing activities	191,252	(18,848)	12,025
Net change in cash and cash equivalents	(2,425)	(3,808)	5,349
Cash and cash equivalents, beginning of year	6,854	10,662	5,313
Cash and cash equivalents, end of year	4,429	6,854	10,662
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for interest, net of capitalized amounts	11,528	6,219	4,072
NON-CASH INVESTING AND FINANCING ACTIVITY
Construction costs payable capitalized to real estate	28,805	37,033	16,142
Accrual of dividends and distributions	$ 41,849	$ 28,104	$ 22,355

Organization

Organization	12 Months Ended
	Dec. 31, 2016
Organization and Description of Business
Organization and Description of Business	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 operating data centers. As of December 31, 2016, the Company owns a 70.7% common interest in our Operating Partnership and affiliates of The Carlyle Group and others own a 29.3% interest in our Operating Partnership. See additional discussion in Note 11, Noncontrolling Interests – Operating Partnership.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
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 our management in accordance with U.S. generally accepted accounting principles (“GAAP”) and in compliance with the rules and regulations of the U.S. Securities and Exchange Commission. Intercompany balances and transactions have been eliminated upon consolidation. In 2016, we adopted ASU 2015-02, Amendments to the Consolidation Analysis. This standard amends certain guidance applicable to the consolidation of various legal entities, including variable interest entities (“VIE”). We evaluated the application of ASU 2015-02 and concluded that no change was required to the accounting for our interest in our Operating Partnership. However, under the new guidance, our Operating Partnership now meets the definition and criteria of a VIE and we are the primary beneficiary of the VIE. Our sole significant asset is the investment in our Operating Partnership, and consequently, substantially all of our assets and liabilities represent those assets and liabilities of our Operating Partnership. Our debt is an obligation of our Operating Partnership where the creditors also have recourse against the credit of the Company. Recent Accounting Pronouncements In January 2017, the FASB issued guidance codified in ASC Topic 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The standard changes the definition of a business to assist entities with evaluating when a set of transferred assets and activities is a business. In accordance with the transition guidance of ASC Topic 2017-01, we early adopted the standard on October 1, 2016. As a result of this new guidance acquisitions may now result in an asset purchase rather than a business combination. In August 2016, the Financial Accounting Standards Board (“FASB”) issued guidance codified in Accounting Standards Codification (“ASC”) Topic 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. The standard provides guidance on eight specific cash flow classification issues including debt prepayment or debt extinguishment costs, contingent consideration payments made after a business combination, and separately identifiable cash flows and application of the predominance principle. The standard will be effective for the fiscal year beginning January 1, 2018, and subsequent interim periods. We do not expect the provisions of ASC 2016-15 to have a material impact on our consolidated financial statements. In March 2016, the FASB issued guidance codified in ASC Topic 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The standard simplifies several aspects related to the accounting for share-based payment transactions, including the accounting for income taxes, statutory tax withholding requirements and classification in the statement of cash flows. The standard will be effective for the fiscal year beginning January 1, 2017 and subsequent interim periods. We do not expect the provisions of ASC 2016-09 to have a material impact on our consolidated financial statements. In February 2016, the FASB issued guidance codified in ASC Topic 842, Leases, which amends the guidance in former ASC 840, Leases. The main principle of ASC 842 requires lessees to recognize the assets and liabilities that arise from nearly all leases on the consolidated balance sheet. Lessor accounting remains mainly consistent with current guidance, with the majority of changes allowing for better alignment with the new lessee model and ASC Topic 606. The standard is effective for interim and annual reporting periods beginning after December 15, 2018, with early adoption permitted. The standard requires a modified retrospective transition approach. In May 2014, the FASB issued guidance codified in ASC Topic 606, Revenue Recognition – Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition. The standard establishes a five-step model framework which recognizes revenue as an entity transfers control of goods or services to customer and requires enhanced disclosures. This standard does not apply to leases, which will be accounted for under ASC Topic 842, Leases. The revenue standard is effective for interim and annual reporting periods beginning after December 15, 2017. The standard permits the use of either the retrospective or cumulative effect transition method. As ASC Topic 606 does not impact lessor accounting, we do not believe this standard will significantly impact our accounting for rental revenue. In addition, we do not anticipate a significant impact to our accounting for power, interconnection, tenant reimbursement and other revenue. We plan to adopt ASC Topic 842 and ASC Topic 606 effective January 1, 2018. As a lessee we do not anticipate the classification of our leases to change, but we will be required to recognize a lease liability and corresponding right-of-use asset on our consolidated balance sheets for all of our operating leases. Using the fixed noncancellable term of all existing data center leases, excluding renewal options, we estimate the initial lease liability and right-of-use asset will be approximately $100 million on our consolidated balance sheet as of December 31, 2016. As we continue to evaluate the provisions of ASC Topic 842, we will evaluate our existing renewal options within our data center leases and ultimately conclude as to whether we are, or are not, reasonably certain, based on relevant factors that may create an economic incentive for us, to exercise renewal options for each of our data center leases. If we determine that we are reasonably certain to exercise all renewal options for each lease, we estimate the initial lease liability and right of use asset will be approximately $300 million on our consolidated balance sheet as of December 31, 2016. Subject to our evaluation of whether we are reasonably certain to exercise renewal options for each of our data center leases as well as resolution of other implementation items, we estimate our straight-line rental expense could increase up to $6 million within our consolidated statement of operations for the year ended December 31, 2016. In accordance with ASC Topic 842, lessor accounting for our leases remains largely unchanged, apart from the narrower scope of initial direct costs that can be capitalized. The new standard defines initial direct costs as only incremental costs of signing a lease. For the year ended December 31, 2016, we estimate that $1 million to $2 million of internal sales employees’ compensation, payroll-related fringe benefits and certain external legal fees related to the execution of successful lease agreements will no longer meet the definition of initial direct costs and will be accounted for as a sales and marketing expense in the consolidated statement of operations upon adoption of ASC Topic 842. We are currently evaluating the other impacts of ASC Topic 842 and ASC Topic 606 on our significant accounting policies and consolidated financial statements. Use of Estimates The preparation of these 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. Investments in Real Estate Real estate investments are carried at cost less accumulated depreciation and amortization. The cost of real estate includes the purchase price of property and leasehold improvements. Expenditures for maintenance and repairs are expensed as incurred. Significant renovations and betterments that extend the economic useful lives of assets are capitalized. During land development and construction periods, we capitalize construction costs, legal fees, financing costs, real estate taxes and insurance, rental expense and internal costs of personnel performing development, if such costs are incremental and identifiable to a specific development project. Capitalization of costs begins upon commencement of development efforts and ceases when the property is ready for its intended use and held available for occupancy. Interest is capitalized during the period of development based upon applying the weighted-average borrowing rate to the actual development costs expended. Capitalized interest costs were $4.1 million, $3.7 million and $4.6 million for the years ended December 31, 2016, 2015, and 2014, respectively. Depreciation and amortization are calculated using the straight‑line method over the following useful lives of the assets: Buildings 27 to 40 years Building improvements 1 to 10 years Leasehold improvements The shorter of the lease term or useful life of the asset Depreciation expense was $89.2 million, $76.1 million and $65.1 million for the years ended December 31, 2016, 2015 and 2014, respectively. Acquisition of Investment in Real Estate When accounting for business combinations and asset acquisitions, the fair value of the real estate acquired is allocated to the acquired tangible assets, consisting primarily of land, building and building improvements, and identified intangible assets and liabilities, consisting of the value of above-market and below-market leases, value of in-place leases and the value of customer relationships. The fair value of the land and building of an acquired property is determined by valuing the property as if it were vacant, and the “as-if-vacant” fair value is then allocated to land and building based on management’s determination of the fair values of these assets. Management determines the as-if-vacant fair value of a property using methods similar to those used by independent appraisers. Factors considered by management in performing these analyses include an estimate of carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases. The fair value of intangibles related to in-place leases includes the value of lease intangibles for above-market and below-market leases, lease origination costs, and customer relationships, determined on a lease-by-lease basis. Above-market and below-market leases are valued based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) management's estimate of fair market lease rates for the corresponding in-place leases, measured over a time period equal to the remaining noncancelable term of the lease and, for below-market leases, over a period equal to the initial term plus any below-market fixed rate renewal periods. Lease origination costs include estimates of costs avoided associated with leasing the property, including tenant allowances and improvements and leasing commissions. Customer relationship intangibles relate to the additional revenue opportunities expected to be generated through interconnection services and utility services to be provided to the in-place lease tenants. The capitalized values for above and below-market lease intangibles, lease origination costs, and customer relationships are amortized over the term of the underlying leases or the expected customer relationship. Amortization related to above-market and below-market leases where the Company is the lessor is recorded as either a reduction of or an increase to rental revenue, amortization related to above-market and below-market leases where the Company is the lessee is recorded as either a reduction of or an increase to rent expense. If a lease is terminated prior to its stated expiration, all unamortized amounts relating to that lease are written off. The carrying value of intangible assets is reviewed for impairment in connection with its respective asset group whenever events or changes in circumstances indicate that the asset group may not be recoverable. An impairment loss is recognized if the carrying amount of the asset group is not recoverable and its carrying amount exceeds its estimated fair value. No impairment loss related to these intangible assets was recognized for the years ended December 31, 2016, 2015, or 2014. The excess of the cost of an acquired business over the net of the amounts assigned to assets acquired (including identified intangible assets) and liabilities assumed is recorded as goodwill. As of December 31, 2016, and 2015, we had approximately $41.2 million of goodwill at each date. The Company’s goodwill has an indeterminate life and is not amortized, but is tested for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the asset might be impaired. No impairment loss was recognized for the years ended December 31, 2016, 2015, or 2014. Cash and Cash Equivalents Cash and cash equivalents include all non‑restricted cash held in financial institutions and other non‑restricted highly liquid short‑term investments with original maturities at acquisition of three months or less. Deferred Costs Deferred leasing costs include commissions paid to third parties, including brokers, leasing agents, referral agents, and internal sales commissions paid to employees for successful execution of lease agreements. These commissions and other direct and incremental costs incurred to obtain new customer leases are capitalized and amortized over the term of the related leases using the straight-line method. If a lease terminates prior to the expiration of its initial term, any unamortized deferred costs related to the lease are written off to amortization expense. Deferred leasing costs are included within other assets in the consolidated balance sheets and consisted of the following, net of amortization, as of December 31, 2016, and 2015 (in thousands): December 31, December 31, 2016 2015 Internal sales commissions $ $ Third party commissions External legal counsel Total $ $ Deferred financing costs include costs incurred in connection with obtaining debt and extending existing debt. These financing costs are capitalized and amortized on a straight-line basis, which approximates the effective-interest method, over the term of the loan and the amortization is included as a component of interest expense. Depending on the type of debt instrument, deferred financing costs are reported either in other assets or as a direct deduction from the carrying amount of the related debt liabilities in our consolidated balance sheets. Recoverability of Long‑Lived Assets We review our long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Impairment is recognized when estimated expected future cash flows (undiscounted and without interest charges) are less than the carrying amount of the assets. The estimation of expected future net cash flows is inherently uncertain and relies, to a considerable extent, on assumptions regarding current and future economics and market conditions and the availability of capital. If, in future periods, there are changes in the estimates or assumptions incorporated into the impairment review analysis, the changes could result in an adjustment to the carrying amount of the long-lived assets. To the extent that impairment has occurred, the excess of the carrying amount of long-lived assets over its estimated fair value would be recognized as an impairment loss charged to net income. For the years ended December 31, 2016, 2015, and 2014, no impairment of long-lived assets was recognized. Derivative Instruments and Hedging Activities We reflect all derivative instruments at fair value as either assets or liabilities on the 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 hedging instruments as a component of accumulated other comprehensive income or loss. Any ineffective portion of a derivative’s change in fair value is immediately recognized within net income. For derivatives that do not meet the criteria for hedge accounting, changes in fair value are immediately recognized within net income. See additional discussion in Note 9 Derivatives and Hedging Activities. Internal-Use Software We recognize internal-use software development costs based on the development stage of the project and nature of the cost. Internal and external costs incurred during the preliminary project stage are expensed as they are incurred. Internal and external costs incurred to develop internal-use software during the application development stage are capitalized. Internal and external training costs and maintenance costs during the post-implementation-operation stage are expensed as incurred. Completed projects are placed into service and amortized over the estimated useful life of the software. For the years ended December 31, 2016, 2015, and 2014, we recorded zero, $0.3 million, and $2.0 million, respectively, related to impairment of internal use software. Revenue Recognition All customer leases are classified as operating leases and minimum rents are recognized on a straight-line basis over the customer’s lease term. The excess of rents recognized over amounts contractually due pursuant to the underlying leases are included in deferred rent receivable, and included in other assets in the consolidated balance sheets. If a lease terminates prior to its stated expiration, the deferred rent receivable relating to that lease is written off as a reduction of rental revenue. When arrangements include multiple elements, the revenue associated with separate elements is allocated based on the relative fair values of those elements. The revenue associated with each element is then recognized as earned. Interconnection services and additional space services are considered as separate earnings processes that are provided and completed on a month-to-month basis and revenue is recognized in the period that services are performed. Customer set-up charges and utility installation fees are initially deferred and recognized over the term of the lease 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, tenant reimbursements or other billed amounts is considered by management to be uncollectible. At December 31, 2016, and 2015, the allowance for doubtful accounts totaled $0.2 million and $0.1 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 the Black-Scholes option-pricing model. The fair value of restricted share-based and Operating Partnership unit compensation is based on the fair value of our common stock on the date of the grant. The fair value of performance share awards, which have a market condition, is based on a Monte Carlo simulation. The fair value for all share-based compensation is amortized on a straight-line basis over the vesting period. Asset Retirement and Environmental Remediation Obligations We record accruals for estimated asset retirement and environmental remediation obligations. The obligations relate primarily to the removal of asbestos 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, 2016, and 2015, the amounts included in unearned revenue, prepaid rent and other liabilities on the consolidated balance sheets were approximately $1.4 million and $1.7 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 generally are not subject to corporate level federal income tax on the earnings distributed currently to our stockholders. If we fail to qualify as a REIT in any taxable year, and are unable to avail ourselves of certain savings provisions set forth in the Code, all of our taxable income would be subject to federal income tax at regular corporate rates, including any applicable alternative minimum tax. To maintain REIT status, we must distribute a minimum of 90% of our taxable income. However, it is our policy and intent, subject to change, to distribute 100% of our taxable income and therefore, no provision is required in the accompanying consolidated financial statements for federal income taxes with regards to activities of the REIT and its subsidiary pass‑through entities. The allocable share of taxable income is included in the income tax returns of its stockholders. The Company is subject to the statutory requirements of the locations in which it conducts business. State and local income taxes are accrued as deemed required in the best judgment of management based on analysis and interpretation of respective tax laws. We have elected to treat certain subsidiaries as a TRS. Certain activities that we undertake must be conducted by a TRS, such as services for our tenants that could be considered otherwise impermissible for us to perform and holding assets that we cannot hold directly. A TRS is subject to corporate level federal and state income taxes. Deferred income taxes are recognized in certain taxable entities. Deferred income tax generally is a function of the period’s temporary differences (items that are treated differently for tax purposes than for financial reporting purposes), the utilization of tax net operating losses generated in prior years that previously had been recognized as deferred income tax assets and the reversal of any previously recorded deferred income tax liabilities. A valuation allowance for deferred income tax assets is provided if we believe all or some portion of the deferred income tax asset may more likely than not be 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, 2016, and 2015, the gross deferred income taxes were not material. We currently have no liabilities for uncertain income tax positions. The earliest tax year for which we are subject to examination is 2013. 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, 2016
Acquisitions
Acquisitions	3. Acquisitions On November 10, 2016, we paid cash consideration of $65.0 million to acquire a 21.75-acre operating light-industrial / flex office park located in Reston, Virginia, referred to as the Reston Campus Expansion. The transaction was accounted for as an asset acquisition. We plan to redevelop the existing buildings into over 611,000 of incremental data center NRSF across multiple phases as existing customers vacate their existing space upon expiration of their leases. The acquisition and redevelopment of the Reston Campus Expansion will extend our position as a multi-tenant data center provider in the Northern Virginia market.

Acquired Intangible Assets and

Acquired Intangible Assets and Liabilities	12 Months Ended
	Dec. 31, 2016
Acquired Intangible Assets and Liabilities
Acquired Intangible Assets and Liabilities	4. Acquired Intangible Assets and Liabilities During the year ended December 31, 2016, through the acquisition of the Reston Campus Expansion, we added $7.5 million of new intangible assets and $0.4 million of new intangible liabilities with a weighted average life of 4.3 years and 5.7 years, respectively. We did not add new intangible assets or liabilities during the year ended December 31, 2015. Above-market and below-market lease intangibles and other intangibles balances at December 31, 2016, and 2015, are as follows (in thousands): December 31, December 31, 2016 2015 Lease contracts above-market value $ $ Accumulated amortization Lease contracts above-market value, net $ $ Lease contracts below-market value $ $ Accumulated amortization Lease contracts below-market value, net $ $ Other identified intangible assets $ $ Accumulated amortization Other identified intangible assets, net $ $ The net effect of amortization of acquired above‑market and below‑market leases resulted in an increase to rental revenue of $0.5 million, $0.5 million, and $0.6 million, for the years ended December 31, 2016, 2015, and 2014, 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, 2017 $ 2018 2019 2020 2021 Thereafter Total $ Amortization of all other identified intangible assets was $2.0 million, $2.0 million, and $3.4 million, for the years ended December 31, 2016, 2015, and 2014, 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, 2017 $ 2018 2019 2020 2021 Thereafter Total $

Investment in Real Estate

Investment in Real Estate	12 Months Ended
	Dec. 31, 2016
Investment in Real Estate
Investment in Real Estate	5. Investment in Real Estate The following is a summary of the properties owned or leased by market at December 31, 2016 (in thousands): Buildings and Construction in Market Land Improvements Progress Total Cost Boston $ $ $ $ Chicago Denver — Los Angeles Miami — New York Northern Virginia San Francisco Bay Total $ $ $ $ In November 2014, the Massachusetts Bay Transportation Authority acquired 52,248 square feet of land at BO1 pursuant to an order of taking. Based on the relative fair value of the parcel, the carrying value of land was allocated to the disposed parcel. The Company recognized a $1.2 million gain on land disposal in the consolidated statements of operations during the period ended December 31, 2014.

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2016
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, 2016, and 2015 (in thousands): December 31, December 31, 2016 2015 Deferred leasing costs $ $ Deferred rent receivable Internal-use software Prepaid expenses Corporate furniture, fixtures and equipment Deferred financing costs Other Total $ $ Deferred leasing costs are amortized as amortization expense on a straight‑line basis over the remaining lease terms 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, 2017 $ 2018 2019 2020 2021 Thereafter Total $

Leases

Leases	12 Months Ended
	Dec. 31, 2016
Leases
Leases	7. Leases The future minimum lease payments to be received under noncancelable operating leases in effect at December 31, 2016, are as follows (in thousands): Year Ending December 31, 2017 $ 2018 2019 2020 2021 Thereafter Total $ 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, CO. The future minimum lease payments to be paid under noncancelable real estate leases in effect at December 31, 2016, are as follows (in thousands): Year Ending December 31, 2017 $ 2018 2019 2020 2021 Thereafter Total $

Debt

Debt	12 Months Ended
	Dec. 31, 2016
Debt
Debt	8. Debt A summary of outstanding indebtedness as of December 31, 2016, and 2015, is as follows (in thousands): Maturity December 31, December 31, Interest Rate Date 2016 2015 Revolving credit facility 2.32% and 1.98% at December 31, 2016, and December 31, 2015, respectively June 24, 2019 $ $ 2019 Senior unsecured term loan (1) 3.23% at December 31, 2016, and December 31, 2015 January 31, 2019 2020 Senior unsecured term loan (2) 2.60% and 2.43% at December 31, 2016, and December 31, 2015 June 24, 2020 2021 Senior unsecured term loan 2.27% at December 31, 2016 February 2, 2021 — 2023 Senior unsecured notes 4.19% at December 31, 2016 June 15, 2023 — Total principal outstanding Unamortized deferred financing costs Total debt $ $ (1) Our Operating Partnership entered into a swap agreement with respect to the 2019 Term Loan (as defined below) to swap the variable interest rate associated with $100 million, or 100%, of the 2019 Term Loan to a fixed rate of approximately 3.23% per annum at our current leverage ratio. See “Derivatives and Hedging Activities” in Note 9 below. (2) Our Operating Partnership entered into a swap agreement with respect to the 2020 Term Loan to swap the variable interest rate associated with $75 million, or 50%, of the principal amount of the 2020 Term Loan (as defined below) to a fixed rate of approximately 2.93% per annum at our current leverage ratio. The interest rate on the remaining $75 million of the 2020 Term Loan is based on LIBOR plus the applicable spread. The effective interest rate as of December 31, 2016, is 2.60%. See “Derivatives and Hedging Activities” in Note 9 below. Revolving Credit Facility On June 24, 2015, our Operating Partnership and certain subsidiary co-borrowers entered into a third amended and restated credit agreement (as amended, the “Credit Agreement”) with a group of lenders for which KeyBank National Association acts as the administrative agent. The Credit Agreement maturity date is June 24, 2019, with a one- time extension option, which, if exercised, would extend the maturity date to June 24, 2020. The exercise of the extension option is subject to the payment of an extension fee equal to 10 basis points of the total commitment under the Credit Agreement at initial maturity and certain other customary conditions. The Credit Agreement includes a total commitment of $500 million, providing for a $350 million revolving credit facility and a $150 million unsecured term loan scheduled to mature on June 24, 2020. See “2020 Senior Unsecured Term Loan” below for a discussion of the $150 million term loan. The Credit Agreement contains an accordion feature, which allows our Operating Partnership to increase the total commitment from $500 million to $700 million, under specified circumstances, including securing capital from new or existing lenders. On February 2, 2016, we partially exercised the Credit Agreement accordion feature and entered into a $100 million senior unsecured term loan, which increased our current commitment under the Credit Agreement from $500 million to $600 million. In addition, the accordion feature increased by $100 million, which allows our Operating Partnership to increase the total commitment from $600 million to $800 million under specified circumstances, including securing capital from new or existing lenders. See “2021 Unsecured Term Loan” below for a discussion of the $100 million senior unsecured term loan. Borrowings under the revolving credit facility bear interest at a variable rate per annum equal to either (i) LIBOR plus 155 basis points to 225 basis points, or (ii) a base rate plus 55 basis points to 125 basis points, each depending on our Operating Partnership's leverage ratio. At December 31, 2016, our Operating Partnership’s leverage ratio was 23.3% and the interest rate was LIBOR plus 155 basis points. The total amount available for borrowing under the revolving credit facility, which is part of the Credit Agreement, is equal to the lesser of $350.0 million or the availability calculated based on our unencumbered asset pool. As of December 31, 2016, the borrowing capacity was $350.0 million. As of December 31, 2016, $194.0 million was borrowed and outstanding, $4.5 million was outstanding under letters of credit and therefore $151.5 million remained available for us to borrow under the revolving credit facility. Our ability to borrow under the Credit Agreement is subject to ongoing compliance with a number of financial covenants and other customary restrictive covenants, including, among others: · a maximum leverage ratio (defined as total consolidated indebtedness to total gross asset value) of 60%, which, as of December 31, 2016, was 23.3%. · a maximum secured debt ratio (defined as total consolidated secured debt to total gross asset value) of 40%, which, as of December 31, 2016, was 0.0%. · a minimum fixed charge coverage ratio (defined as adjusted consolidated earnings before interest, taxes, depreciation and amortization to consolidated fixed charges) of 1.7 to 1.0, which, as of December 31, 2016, was 8.0 to 1.0; and · a maximum unhedged variable rate debt ratio (defined as unhedged variable rate indebtedness to gross asset value) of 30%, which, as of December 31, 2016, our unhedged variable rate debt ratio was 12.3%. As of December 31, 2016, we were in compliance with all of the financial covenants under the Credit Agreement. 2019 Senior Unsecured Term Loan On January 31, 2014, our Operating Partnership and certain subsidiaries entered into a $100 million senior unsecured term loan (as amended, the “2019 Term Loan”). The 2019 Term Loan has a five-year term and contains an accordion feature, which allows our Operating Partnership to increase the total commitments by $100 million, to $200 million under specified circumstances including securing capital from new or existing lenders. The 2019 Term Loan ranks pari passu with the 2020 Term Loan, the 2021 Term Loan, the 2023 Notes and the Credit Agreement and contains the same financial covenants and other customary restrictive covenants. As of December 31, 2016, we were in compliance with all of the financial covenants under the 2019 Term Loan. The borrowings under the 2019 Term Loan bear interest at a variable rate per annum equal to either (i) LIBOR plus 175 basis points to 265 basis points, or (ii) a base rate plus 75 basis points to 165 basis points, each depending on our Operating Partnership’s leverage ratio. At December 31, 2016, our Operating Partnership’s leverage ratio was 23.3% and the interest rate was LIBOR plus 175 basis points. 2020 Senior Unsecured Term Loan On June 24, 2015, in connection with, and pursuant to the terms of, the Credit Agreement, our Operating Partnership and certain subsidiaries entered into a $150 million senior unsecured term loan (the "2020 Term Loan"). The 2020 Term Loan has a five-year term maturing on June 24, 2020. The 2020 Term Loan ranks pari passu with the 2019 Term Loan, the 2021 Term Loan and the 2023 Notes and contains the same financial covenants and other customary restrictive covenants. As of December 31, 2016, we were in compliance with all of the financial covenants under the 2020 Term Loan. The borrowings under the 2020 Term Loan bear interest at a variable rate per annum equal to either (i) LIBOR plus 150 basis points to 220 basis points, or (ii) a base rate plus 50 basis points to 120 basis points, each depending on our Operating Partnership' s leverage ratio. At December 31, 2016, the Operating Partnership's leverage ratio was 23.3% and the interest rate was LIBOR plus 150 basis points. 2021 Senior Unsecured Term Loan On February 2, 2016, pursuant to the terms of the Credit Agreement, we partially exercised the accordion feature and entered into a $100 million senior unsecured term loan (the “2021 Term Loan”). The 2021 Term Loan has a five-year term maturing on February 2, 2021. The 2021 Term Loan ranks pari passu with the 2019 Term Loan, the 2020 Term Loan, the 2023 Notes and the Credit Agreement and contains the same financial covenants and other customary restrictive covenants. As of December 31, 2016, we were in compliance with all of the financial covenants under the 2021 Term Loan. The borrowings under the 2021 Term Loan bear interest at a variable rate per annum equal to either (i) LIBOR plus 150 basis points to 220 basis points, or (ii) a base rate plus 50 basis points to 120 basis points, each depending on our Operating Partnership’s leverage ratio. At December 31, 2016, our Operating Partnership’s leverage ratio was 23.3% and the interest rate was LIBOR plus 150 basis points. 2023 Senior Unsecured Notes On June 15, 2016, our Operating Partnership issued an aggregate principal amount of $150 million, 4.19% senior unsecured notes due June 15, 2023 (the “2023 Notes”) in a private placement to certain accredited investors. The terms of the 2023 Notes are governed by a note purchase agreement, dated June 15, 2016 (the “Note Purchase Agreement”), by and among our Operating Partnership, the Company and the purchasers named therein. Interest is payable semiannually, on the 15 th day of June and December in each year, commencing on December 15, 2016. The 2023 Notes are senior unsecured obligations of our Operating Partnership and are jointly and severally guaranteed by the Company and each of our Operating Partnership’s subsidiaries that guarantees indebtedness under our Operating Partnership’s Credit Agreement (the “Subsidiary Guarantors”). Our Operating Partnership may prepay all or a portion of the 2023 Notes upon notice to the holders for 100% of the principal amount so prepaid plus a make-whole premium as set forth in the Note Purchase Agreement. Upon the occurrence of certain change of control events, holders of the 2023 Notes will have the right to require our Operating Partnership to purchase 100% of such holder’s 2023 Notes in cash at a purchase price equal to 100% of the principal amount thereof plus accrued and unpaid interest, if any, to the date of repurchase. The 2023 Notes rank pari passu with the 2019 Term Loan, the 2020 Term Loan, the 2021 Term Loan and the Credit Agreement. The Note Purchase Agreement contains the same financial covenants as the Credit Agreement, as described above. In addition, certain additional financial covenants in the Credit Agreement were automatically incorporated into the Note Purchase Agreement, and, subject to certain conditions, these additional financial covenants will be deleted, removed, amended or otherwise modified to be more or less restrictive if the analogous covenant in the Credit Agreement is so deleted, removed, amended or otherwise modified. The aforementioned covenants are subject to a number of exceptions and qualifications set forth in the Note Purchase Agreement. As of December 31, 2016, we were in compliance with all of the financial covenants under the Note Purchase Agreement. Debt Maturities The following table summarizes the amount of our outstanding debt and when such debt currently becomes due (in thousands): Year Ending December 31, 2017 $ — 2018 — 2019 2020 2021 Thereafter Total principal outstanding Unamortized deferred financing costs Total debt, net $

Derivatives and Hedging Activit

Derivatives and Hedging Activities	12 Months Ended
	Dec. 31, 2016
Derivatives and Hedging Activities
Derivatives and Hedging Activities	9. Derivatives and Hedging Activities On April 9, 2015, we entered into a $75 million forward starting five-year interest rate swap agreement, effective May 5, 2015, to protect against adverse fluctuation in interest rates. The swap reduces our exposure to variability in cash flows relating to interest payments on $75 million of one-month LIBOR variable rate debt and effectively fixes the interest rate at approximately 2.93% per annum. Also, on February 3, 2014, we entered into a five-year interest rate swap agreement that effectively fixes the interest rate on $100 million of outstanding debt at approximately 3.23% per annum. Both interest rate swap agreements were designated for hedge accounting. Risk Management Objective of Using Derivatives We are exposed to certain risks arising from both our business operations and economic conditions. We principally manage our exposures to a wide variety of business and operational risks through management of our core business activities. We manage economic risks, including interest rate, liquidity, and credit risk primarily by managing the amount, sources, and duration of our debt funding and the use of derivative financial instruments. Specifically, we enter into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known or uncertain cash amounts, the value of which are determined by interest rates. Our derivative financial instruments are used to manage differences in the amount, timing, and duration of our known or expected cash receipts and our known or expected cash payments principally related to our investments and borrowings. Cash Flow Hedges of Interest Rate Risk Our objectives in using interest rate derivatives are to reduce variability in interest expense and to manage our exposure to adverse interest rate movements. To accomplish this objective, we primarily use interest rate swaps as part of our interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable amounts from a counterparty in exchange for the Company making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income or loss on the consolidated balance sheets and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. The amounts recorded in other comprehensive income related to the unrealized loss on derivative contracts of $1.1 million, $2.4 million, and $1.4 million for the years ended December 31, 2016, 2015, and 2014, respectively. The amounts reclassified from other comprehensive income to interest expense on the consolidated statements of operations were $1.7 million, $1.9 million, and $1.1 million for the years ended December 31, 2016, 2015, and 2014, respectively. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings. During the years ended December 31, 2016, 2015, and 2014, we did not record any amount in earnings related to derivatives as there was no hedge ineffectiveness. Amounts reported in accumulated other comprehensive income or loss related to derivatives will be reclassified to interest expense as interest payments are made on our variable-rate debt. During the subsequent twelve months, beginning January 1, 2017, we estimate that $0.9 million will be reclassified as an increase to interest expense. Derivatives are recorded at fair value in our consolidated balance sheets in other assets or unearned revenue, prepaid rent and other liabilities, as applicable. We do not net our derivative position by counterparty for purposes of balance sheet presentation and disclosure. We had a $0.4 million and $0.8 million in derivative liabilities recognized in unearned revenue, prepaid rent and other liabilities in our consolidated balance sheets as of December 31, 2016 and 2015, respectively. We also had a $0.3 million derivative asset recognized in other assets in our consolidated balance sheet as of December 31, 2016. We had no derivative assets recognized in other assets in our consolidated balance sheet as of December 31, 2015.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity
Stockholders' Equity	10. Stockholders’ Equity At December 31, 2016, 120 million shares were authorized to be issued by the Company, 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, 2016, we had 33.9 million shares of common stock issued and outstanding. Since our initial public offering (“IPO”), we have issued common stock under our 2010 Equity Incentive Award 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 Award Plan, we received proceeds (made payments) from the exercise of stock options, net of settlements, of $1.3 million, ($2.9) million, and $0.9 million for the years ended December 31, 2016, 2015, and 2014, respectively. Also, we issued shares of common stock as restricted stock award and performance stock award grants, net of forfeitures, and option exercises, net of settlements, in the amount of 239,068, 393,337 and 370,214 during the years ended December 31, 2016, 2015, and 2014, respectively. See Note 12, Equity Incentive Award Plan, for additional information on our 2010 Equity Incentive Award Plan. During the year ended December 31, 2016, and 2015, 3,007,000 and 8,500,000 common Operating Partnership units held by the Carlyle Group and other third parties were redeemed for shares of our common stock in connection with the offer and sale of 3,007,000 and 8,500,000 shares of our common stock, respectively. See Note 11, Noncontrolling Interests – Operating Partnership, for additional information. 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 a 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 2016, 2015, and 2014, we paid all our dividends in cash. The following summarizes the taxability of our common and preferred stock dividends per share for the years then ended: Year Ended December 31, Record Date 2016 2015 2014 Common Stock: Ordinary income $ $ $ Qualified dividend — — — Capital gains — — — Return of capital — — — Total dividend (1) $ $ $ Preferred Stock: Ordinary income $ $ $ Qualified dividend — — — Capital gains — — — Total dividend (2) $ $ $ (1) Of the $2.36 taxable dividend in 2016, $0.80 was paid in January 2017, of which $0.44 will apply to tax year 2017. Of the $1.70 taxable dividend in 2015, $0.53 was paid in January 2016, of which $0.41 will apply to tax year 2016. Of the $1.15 taxable dividends in 2014, $0.42 was paid in January 2015, of which $0.32 applies to tax year 2015. (2) Of the $1.81 taxable dividend in 2016, $0.45 was paid in January 2017. Of the $1.81 taxable dividend in 2015, $0.45 was paid in January 2016. Of the $1.81 taxable dividend in 2014, $0.45 was paid in January 2015. In order to comply with the real estate investment trust requirements of the 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 taxable 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 federal tax return for the year ended December 31, 2016 has not been filed. The taxability information presented for our dividends paid in 2016 is based upon management’s estimates.

Noncontrolling Interests - Oper

Noncontrolling Interests - Operating Partnership	12 Months Ended
	Dec. 31, 2016
Noncontrolling Interests - Operating Partnership
Noncontrolling Interests - Operating Partnership	11. Noncontrolling Interests — Operating Partnership Noncontrolling interests represent the limited partnership interests in our Operating Partnership held by individuals and entities other than CoreSite Realty Corporation. The current holders of common Operating Partnership units are eligible to have the common Operating Partnership units redeemed for cash or common stock on a one‑for‑one basis, at our option. In connection with the issuance of our 7.25% Series A cumulative redeemable preferred stock on December 12, 2012, our Operating Partnership issued 4,600,000 7.25% Series A cumulative redeemable preferred Operating Partnership units to us. Preferred Operating Partnership units rank senior to the common Operating Partnership units held by both us and noncontrolling interests. The following table shows the ownership interests in our Operating Partnership as of December 31, 2016, and 2015: December 31, 2016 December 31, 2015 Number of Units Percentage of Total Number of Units Percentage of Total CoreSite Realty Corporation % % Noncontrolling interests Total % % For each share of common stock issued by us, our Operating Partnership issues to us an equivalent common Operating Partnership unit. During the year ended December 31, 2016, we issued 233,012 shares of common stock related to employee compensation arrangements and therefore an equivalent number of common Operating Partnership units were issued to us by our Operating Partnership. Holders of common Operating Partnership units of record as of March 31, 2016, June 30, 2016, and September 30, 2016, received quarterly distributions of $0.53 per unit payable in correlation with declared dividends on common stock. Holders of common Operating Partnership units of record as of December 30, 2016, received quarterly distributions of $0.80 per unit payable in correlation with declared dividends on common stock. During the year ended December 31, 2016, 3,007,000 common Operating Partnership units held by The Carlyle Group and other third parties were redeemed for shares of our common stock in connection with the sale of 3,007,000 shares of our common stock. This redemption was recorded as a $37.4 million reduction to noncontrolling interests in our Operating Partnership and an increase to total stockholder’s equity in the consolidated balance sheets. During the year ended December 31, 2015, 8,500,000 common Operating Partnership units held by The Carlyle Group were redeemed for shares of our common stock in connection with the sale of 8,500,000 shares of our common stock. This redemption was recorded as a $110.2 million reduction to noncontrolling interests in our Operating Partnership and an increase to total stockholder’s equity in the consolidated balance sheets. The redemption value of the noncontrolling interests at December 31, 2016, was $1.1 billion based on the closing price of the Company’s common stock of $79.37 on that date.

Equity Incentive Award Plan

Equity Incentive Award Plan	12 Months Ended
	Dec. 31, 2016
Equity Incentive Award Plan
Equity Incentive Plan	12. Equity Incentive Award Plan Our Board of Directors adopted and, with the approval of our stockholders, amended the 2010 Equity Incentive Award Plan (as amended, the “2010 Plan”). The 2010 Plan is administered by the Compensation Committee of the Board of Directors. Awards issuable under the 2010 Plan include common stock, stock options, restricted stock, stock appreciation rights, dividend equivalents, Operating Partnership units and other incentive awards. We have reserved a total of 6,000,000 shares of our common stock for issuance pursuant to the 2010 Plan, which may be adjusted for changes in our capitalization and certain corporate transactions. To the extent that an award expires, terminates or lapses, or an award is settled in cash without the delivery of shares of common stock to the participant, then any unvested shares subject to the award will be available for future grant or sale under the 2010 Plan. Shares of restricted stock which are forfeited or repurchased by us pursuant to the 2010 Plan may again be awarded under the 2010 Plan. The payment of dividend equivalents in cash in conjunction with any outstanding awards will not be counted against the shares available for issuance under the 2010 Plan. As of December 31, 2016, 3,109,189 shares of our common stock were available for issuance pursuant to the 2010 Plan. Stock Options Stock option awards are granted with an exercise price equal to the closing market price of the Company’s common stock on the date of grant. The fair value of each option granted under the 2010 Plan is estimated on the date of grant using the Black‑Scholes option‑pricing model. The fair values are amortized on a straight‑line basis over the vesting periods. Stock options have not been granted since the year ending December 31, 2013. The following table sets forth stock option activity under the 2010 Plan for the years ended December 31, 2016, 2015, and 2014. Number of Weighted Weighted Aggregate Options outstanding, December 31, 2013 $ 7.6 years $14.0 million Granted — — Exercised $5.6 million Forfeited Expired Options outstanding, December 31, 2014 $ 6.7 years $13.7 million Granted — — Exercised $12.0 million Forfeited Expired Options outstanding, December 31, 2015 $ 5.8 years $11.9 million Granted — — Exercised $3.8 million Forfeited — — Expired — — Options outstanding, December 31, 2016 $ 5.0 years $15.0 million Exercisable at December 31, 2014 $ 6.4 years $9.6 million 2015 $ 5.4 years $9.0 million 2016 $ 4.9 years $14.2 million The following table sets forth the number of shares subject to options that are unvested as of December 31, 2016, 2015, and 2014, and the fair value of these options at the grant date: Number of Weighted Unvested balance, December 31, 2013 $ Granted — — Forfeited Vested Unvested balance, December 31, 2014 $ Granted — — Forfeited Vested Unvested balance, December 31, 2015 $ Granted — — Forfeited — — Vested Unvested balance, December 31, 2016 $ As of December 31, 2016, total unearned compensation on options was less than $0.1 million, and the weighted-average vesting period was 0.2 years. 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. No options were granted during the years ended 2016, 2015 or 2014. Restricted Awards and Units Restricted stock awards and restricted stock units, or RSUs, are granted with a fair value equal to the closing market price of the Company's common stock on the date of grant. The principal difference between restricted stock awards and RSUs is that RSUs are not shares of our common stock and do not have any of the rights or privileges thereof, including voting rights. On the applicable vesting date, the holder of an RSU becomes entitled to a share of common stock. The restricted stock awards and RSUs are amortized on a straight-line basis to expense over the vesting period. The following table sets forth the number of unvested restricted stock awards and RSUs and the weighted-average fair value of these awards at the date of grant: Restricted Weighted Unvested balance, December 31, 2013 $ Granted Forfeited Vested Unvested balance, December 31, 2014 $ Granted Forfeited Vested Unvested balance, December 31, 2015 $ Granted Forfeited Vested Unvested balance, December 31, 2016 $ As of December 31, 2016, total unearned compensation on restricted awards was approximately $12.3 million, and the weighted-average vesting period was 2.5 years. Performance Stock Awards We grant long-term incentives to members of management in the form of performance-based restricted stock awards (“PSAs”) under the 2010 Plan. The number of PSAs earned is based on our achievement of relative total shareholder return (“TSR”) measured versus the MSCI US REIT Index over a three-year performance period and ranges between 0% and 150% of a target number of shares for PSAs granted in 2014 and between 25% and 175% of the target for PSAs granted in 2015 and 2016. The PSAs are earned as follows: (i) 20% of the PSAs are eligible to be earned upon TSR achievement in year one of the performance period, (ii) 20% of the PSAs are eligible to be earned upon TSR achievement in year two of the performance period, (iii) 20% of the PSAs are eligible to be earned upon TSR achievement in year three of the performance period, and (iv) 40% of the PSAs are eligible to be earned upon a cumulative TSR achievement over the three-year performance period. The PSAs are granted at the maximum percentage of target and are retired annually to the extent we do not achieve maximum relative TSR versus the MSCI US REIT Index. The PSAs have a service condition and will be released at the end of the three-year performance period, to the extent earned, provided that the holder continues to be employed by the Company at the end of the three-year performance period. The PSAs are amortized on a straight-line basis over the vesting period. Holders of the PSAs are entitled to dividends on the PSAs, which will be accrued and paid in cash at the end of the three-year performance period. The following table sets forth the number of unvested PSAs and the weighted-average fair value of these awards at the date of grant: Weighted- Average Fair Performance-Based Restricted Stock Awards Value at Grant Minimum Maximum Target Date Unvested balance, December 31, 2013 — — — $ — Granted — Performance adjustment — — — — Forfeited — Vested — — — Unvested balance, December 31, 2014 — $ Granted Performance adjustment — Forfeited Vested Unvested balance, December 31, 2015 $ Granted Performance adjustment — — Forfeited Vested Unvested balance, December 31, 2016 $ As of December 31, 2016, total unearned compensation on PSAs was approximately $2.9 million, and the weighted-average vesting period was 2.0 years. The fair value of each PSA award is estimated on the date of grant using a Monte Carlo simulation. The simulation requires assumptions for expected volatility, risk-free rate of return, and dividend yield. The following table summarizes the assumptions used to value the PSAs granted during the years ended December 31, 2016, 2015 and 2014: 2016 2015 2014 Expected term (in years) Expected volatility % % % Expected annual dividend(1) — — — Risk-free rate % % % ______________________ (1) The fair value of the PSAs assumes reinvestment of dividends.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share
Earnings Per Share	13. Earnings Per Share Basic net income per share is calculated by dividing the net income attributable to common shares by the weighted-average number of common shares outstanding during the period. Diluted net income per share adjusts basic net income per share for the effects of potentially dilutive common shares, if the effect is not antidilutive. Potentially dilutive common stock consists of shares issuable under the 2010 Plan. The following is a summary of basic and diluted net income per share (in thousands, except share and per share amounts): Year Ended December 31, 2016 2015 2014 Net income attributable to common shares $ $ $ Weighted-average common shares outstanding - basic Effect of potentially dilutive common shares: Stock options Unvested awards Weighted-average common shares outstanding - diluted Net income per share attributable to common shares Basic $ $ $ Diluted $ $ $ In the calculations above, we have excluded weighted-average potentially dilutive securities of 29,618, 117,048 and 180,020 for the years ended December 31, 2016, 2015, and 2014, respectively, as their effect would have been antidilutive.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2016
Employee Benefit Plan
Employee Benefit Plan	14. Employee Benefit Plan We have a tax qualified retirement 401(k) plan that provides employees with an opportunity to save for retirement on a tax advantaged basis. Employees are eligible to participate after one month of employment. Additionally, after six months of employment, we provide a safe harbor contribution equal to 3% of the participant’s annual salary. The employee and employer contributions are limited to the maximum amount allowed by the Internal Revenue Service. Both employee and employer contributions vest immediately. For the years ended December 31, 2016, 2015, and 2014, our contributions were $0.9 million, $0.8 million, and $0.8 million, respectively.

Estimated Fair Value of Financi

Estimated Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2016
Estimated Fair Value of Financial Instruments
Estimated Fair Value of Financial Instruments	15. Estimated Fair Value of Financial Instruments Authoritative guidance issued by FASB establishes a hierarchy of valuation techniques based on the observability of inputs utilized in measuring assets and liabilities at fair values. This hierarchy establishes market‑based or observable inputs as the preferred source of values, followed by valuation models using management assumptions in the absence of market inputs. The three levels of the hierarchy under the authoritative guidance are as follows: Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the assessment date. Level 2 — Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 3 — Unobservable inputs for the asset or liability. Our financial instruments consist of cash and cash equivalents, accounts and other receivables, interest rate swaps, the revolving credit facility, the senior unsecured term loans, senior unsecured notes, interest payable and accounts payable. The carrying values of cash and cash equivalents, accounts and other receivables, interest payable and accounts payable approximate fair values due to the short-term nature of these financial instruments. The interest rate swaps are recorded at fair value. The valuation of our derivatives is determined using widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative, which reflects the contractual terms of the derivatives, including the period to maturity, and uses observable market-based inputs, including interest rate curves. We have determined that the majority of the inputs used to value our derivatives fall within Level 2 of the fair value hierarchy; however, the credit valuation adjustments associated with our derivatives utilize Level 3 inputs, such as estimates of current credit spreads, to evaluate the likelihood of default by our Operating Partnership and its counterparties. As of December 31, 2016, we have assessed the significance of the impact of the credit valuation adjustments on the overall valuation of our derivative positions and have determined that the credit valuation adjustment is not significant to the overall valuation of our derivative portfolio. As a result we classify our derivative valuation in Level 2 of the fair value hierarchy The total principal balance of our revolving credit facility, senior unsecured term loans, and senior unsecured term notes was $694.0 million and $392.3 million as of December 31, 2016 and 2015, respectively, with a fair value of $673.0 million and $393.0 million, respectively, based on Level 3 inputs from the fair value hierarchy. Under the discounted cash flow method, the fair values of the revolving credit facility, and the senior unsecured term loans are based on our assumptions of market interest rates and terms available incorporating our credit risk for similar loan maturities.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies.
Commitments and Contingencies	16. Commitments and Contingencies Our properties require periodic investments of capital for general capital improvements and for tenant related capital expenditures. We enter into various construction and equipment contracts with third parties for the development of our properties. At December 31, 2016, we had open commitments related to construction contracts of approximately $18.6 million. Additionally, we have commitments related to telecommunications capacity used to connect data centers located within the same market or geographical area, power usage, and company-wide improvements that are ancillary to revenue generation. At December 31, 2016, we had open commitments related to these contracts of approximately $10.3 million. We have agreed with affiliates of the Carlyle Group 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, September 23, 2017, 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. We entered into a Memorandum of Understanding with the Virginia Economic Development Partnership Authority (the “Virginia Memorandum of Understanding”) pursuant to which we are afforded the opportunity to benefit from an exemption from sales and use tax for certain qualifying data center related purchases and equipment leases. This exemption also extends to our customers who execute a Landlord-Tenant Participation Agreement under the Virginia Memorandum of Understanding. The Virginia Memorandum of Understanding establishes thresholds relating to the level of capital investment and qualifying new jobs created within the Commonwealth of Virginia by us and our customers who have agreed to sign participation agreements. In the event those thresholds are not met as of the agreed upon performance date of June 1, 2017, we would be required to repay the sales and use tax benefit we have received, as well as any tax benefit received by our customers who default on their obligation to repay the tax benefit they have received under the exemption program up to a maximum of $7.5 million. We estimate that we may be required to repay between $0.0 million and $4.0 million for sales and use tax benefits we have received under the exemption program, of which none has been accrued in accounts payable and accrued expenses in our consolidated balance sheets as of December 31, 2016, and 2015, as we believe we will meet the thresholds as of the performance date. In the ordinary course of business, we are subject to claims and administrative proceedings. Except as described below, we are not presently party to any proceeding, which we believe to be material or which we would expect to have, individually or in the aggregate, a material adverse effect on our business, financial condition, cash flows or results of operations. On February 4, 2014, U.S. Colo, LLC ("U.S. Colo"), a current customer, filed a complaint against us in the United States District Court for the Central District of California. In the complaint, U.S. Colo alleged that it should not have been charged for the use of various interconnection services under the terms of an existing agreement between the parties. On July 23, 2015, after amendments to the complaint, dismissal of several of U.S. Colo's claims, and a remand of the case to the Superior Court of the State of California, County of Los Angeles (the “Superior Court”), U.S. Colo filed an amended complaint alleging breach of contract and breach of the covenant of good faith and fair dealing. The amended complaint seeks $802,564 in damages for charges paid to us for interconnection services; $70,080,000 in damages for alleged losses of revenue and profits; attorney's fees, interest, and costs of the suit; and declaratory and injunctive relief. On February 4, 2016, the Superior Court granted our motion for summary adjudication, finding that U.S.Colo had contractually waived all claims for lost revenue or profits or other consequential damages. The case was set to start trial on August 29, 2016, but upon unopposed application, the Superior Court vacated the August 29, 2016, trial date, continued the trial date to July 24, 2017, set a final status conference for July 14, 2017, and reset other procedural deadlines in the action. We intend to vigorously defend this legal proceeding. On July 9, 2015, a purported class action lawsuit was filed in the Superior Court of the State of California, County of Los Angeles, against us, alleging various employment law violations related to overtime, meal and break periods, minimum wage, timely payment of wages, wage statements, payroll records and business expenses. On March 15, 2016, we filed a responsive pleading generally denying the allegations. On July 27, 2016, the parties entered into a Memorandum of Understanding, pursuant to which the parties agreed to settle the lawsuit. The settlement, which remains subject to Superior Court approval, resolves the matter on a class-wide basis, on behalf of all non-exempt employees in California, as well a related class action lawsuit filed on July 22, 2016, alleging similar claims, in exchange for a $600,000 payment to be made by us. We anticipate that a hearing for Superior Court approval of the settlement will occur during the first half of 2017. There can be no assurance that the settlement will be finally approved by the Superior Court. We intend to vigorously defend this legal proceeding if the settlement is not approved. While it is not feasible to predict or determine the outcome of these legal proceedings, as of December 31, 2016, we estimate that the ultimate resolution of these litigation matters and other disputes could result in a loss that is reasonably possible between $0.6 million and $3.1 million in the aggregate, of which $2.9 million has been accrued in accounts payable and accrued expenses in our consolidated balance sheet as of December 31, 2016.

Quarterly Financial Information

Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information (unaudited)
Quarterly Financial Information (unaudited)	17. Quarterly Financial Information (unaudited) The table below reflects the selected quarterly information for the years ended December 31, 2016, and 2015 (in thousands except share data): Three Months Ended December 31, September 30, June 30, March 31, 2016 2016 2016 2016 Revenue $ $ $ $ Operating income Net income Net income attributable to common shares Net income per share attributable to common shares - basic $ $ $ $ Net income per share attributable to common shares - diluted $ $ $ $ Three Months Ended December 31, September 30, June 30, March 31, 2015 2015 2015 2015 Revenue $ $ $ $ Operating income Net income Net income attributable to common shares Net income per share attributable to common shares - basic $ $ $ $ Net income per share attributable to common shares - diluted $ $ $ $

Schedule III Real Estate and Ac

Schedule III Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2016
Schedule III Real Estate and Accumulated Depreciation
Schedule III Real Estate and Accumulated Depreciation	CoreSite Realty Corporation Schedule II Real Estate and Accumulated Depreciation December 31, 2016 Gross Amount Carried at Initial Cost Costs Capitalized December 31, 2016 Accumulated Year Building and Subsequent to Building and Depreciation at Acquired Property Name Location Land Improvements Acquisition Land Improvements Total December 31, 2016 or Leased (In thousands) BO1 Somerville, MA $ $ $ $ $ $ $ 2007 CH1 Chicago, IL 2010 DC1 Washington, DC — — 2010 DE1 Denver, CO — — 2012 DE2 Denver, CO — — 2012 LA1 Los Angeles, CA — — 2010 LA2 Los Angeles, CA 2010 MI1 Miami, FL 2010 NY1 New York, NY — — — 2007 NY2 Secaucus, NJ 2013 SV1 San Jose, CA 2010 SV2 Milpitas, CA 2006 SV3 Santa Clara, CA 2007 SV4 Santa Clara, CA 2007 SV5 Santa Clara, CA — 2007 SV6 Santa Clara, CA — 2007 SV7 Santa Clara, CA — 2007 VA1 Reston, VA 2007 VA2 Reston, VA — 2007 Reston Campus Expansion Reston, VA 2016 Total $ $ $ $ $ $ $ None of our properties are encumbered. The aggregate cost of the total properties for federal income tax purposes was approximately $1,592.6 million (unaudited) at December 31, 2016. See accompanying report of independent registered public accounting firm. CoreSite Realty Corporation Schedule III Real Estate and Accumulated Depreciation (Continued) December 31, 2016 The following table reconciles the historical cost and accumulated depreciation of our properties for the years ended December 31, 2016, 2015, and 2014: Year Ended December 31, 2016 2015 2014 (In thousands) Property Balance, beginning of year $ $ $ Additions - property acquisitions — — Additions - improvements Deduction - cost of land disposal — — Balance, end of year $ $ $ Accumulated Depreciation Balance, beginning of year $ $ $ Additions, net of disposals Balance, end of year $ $ $ See accompanying report of independent registered public accounting firm.

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
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 our management in accordance with U.S. generally accepted accounting principles (“GAAP”) and in compliance with the rules and regulations of the U.S. Securities and Exchange Commission. Intercompany balances and transactions have been eliminated upon consolidation. In 2016, we adopted ASU 2015-02, Amendments to the Consolidation Analysis. This standard amends certain guidance applicable to the consolidation of various legal entities, including variable interest entities (“VIE”). We evaluated the application of ASU 2015-02 and concluded that no change was required to the accounting for our interest in our Operating Partnership. However, under the new guidance, our Operating Partnership now meets the definition and criteria of a VIE and we are the primary beneficiary of the VIE. Our sole significant asset is the investment in our Operating Partnership, and consequently, substantially all of our assets and liabilities represent those assets and liabilities of our Operating Partnership. Our debt is an obligation of our Operating Partnership where the creditors also have recourse against the credit of the Company.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In January 2017, the FASB issued guidance codified in ASC Topic 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The standard changes the definition of a business to assist entities with evaluating when a set of transferred assets and activities is a business. In accordance with the transition guidance of ASC Topic 2017-01, we early adopted the standard on October 1, 2016. As a result of this new guidance acquisitions may now result in an asset purchase rather than a business combination. In August 2016, the Financial Accounting Standards Board (“FASB”) issued guidance codified in Accounting Standards Codification (“ASC”) Topic 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. The standard provides guidance on eight specific cash flow classification issues including debt prepayment or debt extinguishment costs, contingent consideration payments made after a business combination, and separately identifiable cash flows and application of the predominance principle. The standard will be effective for the fiscal year beginning January 1, 2018, and subsequent interim periods. We do not expect the provisions of ASC 2016-15 to have a material impact on our consolidated financial statements. In March 2016, the FASB issued guidance codified in ASC Topic 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The standard simplifies several aspects related to the accounting for share-based payment transactions, including the accounting for income taxes, statutory tax withholding requirements and classification in the statement of cash flows. The standard will be effective for the fiscal year beginning January 1, 2017 and subsequent interim periods. We do not expect the provisions of ASC 2016-09 to have a material impact on our consolidated financial statements. In February 2016, the FASB issued guidance codified in ASC Topic 842, Leases, which amends the guidance in former ASC 840, Leases. The main principle of ASC 842 requires lessees to recognize the assets and liabilities that arise from nearly all leases on the consolidated balance sheet. Lessor accounting remains mainly consistent with current guidance, with the majority of changes allowing for better alignment with the new lessee model and ASC Topic 606. The standard is effective for interim and annual reporting periods beginning after December 15, 2018, with early adoption permitted. The standard requires a modified retrospective transition approach. In May 2014, the FASB issued guidance codified in ASC Topic 606, Revenue Recognition – Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition. The standard establishes a five-step model framework which recognizes revenue as an entity transfers control of goods or services to customer and requires enhanced disclosures. This standard does not apply to leases, which will be accounted for under ASC Topic 842, Leases. The revenue standard is effective for interim and annual reporting periods beginning after December 15, 2017. The standard permits the use of either the retrospective or cumulative effect transition method. As ASC Topic 606 does not impact lessor accounting, we do not believe this standard will significantly impact our accounting for rental revenue. In addition, we do not anticipate a significant impact to our accounting for power, interconnection, tenant reimbursement and other revenue. We plan to adopt ASC Topic 842 and ASC Topic 606 effective January 1, 2018. As a lessee we do not anticipate the classification of our leases to change, but we will be required to recognize a lease liability and corresponding right-of-use asset on our consolidated balance sheets for all of our operating leases. Using the fixed noncancellable term of all existing data center leases, excluding renewal options, we estimate the initial lease liability and right-of-use asset will be approximately $100 million on our consolidated balance sheet as of December 31, 2016. As we continue to evaluate the provisions of ASC Topic 842, we will evaluate our existing renewal options within our data center leases and ultimately conclude as to whether we are, or are not, reasonably certain, based on relevant factors that may create an economic incentive for us, to exercise renewal options for each of our data center leases. If we determine that we are reasonably certain to exercise all renewal options for each lease, we estimate the initial lease liability and right of use asset will be approximately $300 million on our consolidated balance sheet as of December 31, 2016. Subject to our evaluation of whether we are reasonably certain to exercise renewal options for each of our data center leases as well as resolution of other implementation items, we estimate our straight-line rental expense could increase up to $6 million within our consolidated statement of operations for the year ended December 31, 2016. In accordance with ASC Topic 842, lessor accounting for our leases remains largely unchanged, apart from the narrower scope of initial direct costs that can be capitalized. The new standard defines initial direct costs as only incremental costs of signing a lease. For the year ended December 31, 2016, we estimate that $1 million to $2 million of internal sales employees’ compensation, payroll-related fringe benefits and certain external legal fees related to the execution of successful lease agreements will no longer meet the definition of initial direct costs and will be accounted for as a sales and marketing expense in the consolidated statement of operations upon adoption of ASC Topic 842. We are currently evaluating the other impacts of ASC Topic 842 and ASC Topic 606 on our significant accounting policies and consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of these 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.
Investments in Real Estate	Investments in Real Estate Real estate investments are carried at cost less accumulated depreciation and amortization. The cost of real estate includes the purchase price of property and leasehold improvements. Expenditures for maintenance and repairs are expensed as incurred. Significant renovations and betterments that extend the economic useful lives of assets are capitalized. During land development and construction periods, we capitalize construction costs, legal fees, financing costs, real estate taxes and insurance, rental expense and internal costs of personnel performing development, if such costs are incremental and identifiable to a specific development project. Capitalization of costs begins upon commencement of development efforts and ceases when the property is ready for its intended use and held available for occupancy. Interest is capitalized during the period of development based upon applying the weighted-average borrowing rate to the actual development costs expended. Capitalized interest costs were $4.1 million, $3.7 million and $4.6 million for the years ended December 31, 2016, 2015, and 2014, respectively. Depreciation and amortization are calculated using the straight‑line method over the following useful lives of the assets: Buildings 27 to 40 years Building improvements 1 to 10 years Leasehold improvements The shorter of the lease term or useful life of the asset Depreciation expense was $89.2 million, $76.1 million and $65.1 million for the years ended December 31, 2016, 2015 and 2014, respectively.
Acquisition of Investment in Real Estate	Acquisition of Investment in Real Estate When accounting for business combinations and asset acquisitions, the fair value of the real estate acquired is allocated to the acquired tangible assets, consisting primarily of land, building and building improvements, and identified intangible assets and liabilities, consisting of the value of above-market and below-market leases, value of in-place leases and the value of customer relationships. The fair value of the land and building of an acquired property is determined by valuing the property as if it were vacant, and the “as-if-vacant” fair value is then allocated to land and building based on management’s determination of the fair values of these assets. Management determines the as-if-vacant fair value of a property using methods similar to those used by independent appraisers. Factors considered by management in performing these analyses include an estimate of carrying costs during the expected lease-up periods considering current market conditions and costs to execute similar leases. The fair value of intangibles related to in-place leases includes the value of lease intangibles for above-market and below-market leases, lease origination costs, and customer relationships, determined on a lease-by-lease basis. Above-market and below-market leases are valued based on the present value (using an interest rate which reflects the risks associated with the leases acquired) of the difference between (i) the contractual amounts to be paid pursuant to the in-place leases and (ii) management's estimate of fair market lease rates for the corresponding in-place leases, measured over a time period equal to the remaining noncancelable term of the lease and, for below-market leases, over a period equal to the initial term plus any below-market fixed rate renewal periods. Lease origination costs include estimates of costs avoided associated with leasing the property, including tenant allowances and improvements and leasing commissions. Customer relationship intangibles relate to the additional revenue opportunities expected to be generated through interconnection services and utility services to be provided to the in-place lease tenants. The capitalized values for above and below-market lease intangibles, lease origination costs, and customer relationships are amortized over the term of the underlying leases or the expected customer relationship. Amortization related to above-market and below-market leases where the Company is the lessor is recorded as either a reduction of or an increase to rental revenue, amortization related to above-market and below-market leases where the Company is the lessee is recorded as either a reduction of or an increase to rent expense. If a lease is terminated prior to its stated expiration, all unamortized amounts relating to that lease are written off. The carrying value of intangible assets is reviewed for impairment in connection with its respective asset group whenever events or changes in circumstances indicate that the asset group may not be recoverable. An impairment loss is recognized if the carrying amount of the asset group is not recoverable and its carrying amount exceeds its estimated fair value. No impairment loss related to these intangible assets was recognized for the years ended December 31, 2016, 2015, or 2014. The excess of the cost of an acquired business over the net of the amounts assigned to assets acquired (including identified intangible assets) and liabilities assumed is recorded as goodwill. As of December 31, 2016, and 2015, we had approximately $41.2 million of goodwill at each date. The Company’s goodwill has an indeterminate life and is not amortized, but is tested for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the asset might be impaired. No impairment loss was recognized for the years ended December 31, 2016, 2015, or 2014.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include all non‑restricted cash held in financial institutions and other non‑restricted highly liquid short‑term investments with original maturities at acquisition of three months or less.
Deferred Costs	Deferred Costs Deferred leasing costs include commissions paid to third parties, including brokers, leasing agents, referral agents, and internal sales commissions paid to employees for successful execution of lease agreements. These commissions and other direct and incremental costs incurred to obtain new customer leases are capitalized and amortized over the term of the related leases using the straight-line method. If a lease terminates prior to the expiration of its initial term, any unamortized deferred costs related to the lease are written off to amortization expense. Deferred leasing costs are included within other assets in the consolidated balance sheets and consisted of the following, net of amortization, as of December 31, 2016, and 2015 (in thousands): December 31, December 31, 2016 2015 Internal sales commissions $ $ Third party commissions External legal counsel Total $ $ Deferred financing costs include costs incurred in connection with obtaining debt and extending existing debt. These financing costs are capitalized and amortized on a straight-line basis, which approximates the effective-interest method, over the term of the loan and the amortization is included as a component of interest expense. Depending on the type of debt instrument, deferred financing costs are reported either in other assets or as a direct deduction from the carrying amount of the related debt liabilities in our consolidated balance sheets.
Recoverability of Long-Lived Assets	Recoverability of Long‑Lived Assets We review our long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Impairment is recognized when estimated expected future cash flows (undiscounted and without interest charges) are less than the carrying amount of the assets. The estimation of expected future net cash flows is inherently uncertain and relies, to a considerable extent, on assumptions regarding current and future economics and market conditions and the availability of capital. If, in future periods, there are changes in the estimates or assumptions incorporated into the impairment review analysis, the changes could result in an adjustment to the carrying amount of the long-lived assets. To the extent that impairment has occurred, the excess of the carrying amount of long-lived assets over its estimated fair value would be recognized as an impairment loss charged to net income. For the years ended December 31, 2016, 2015, and 2014, no impairment of long-lived assets was recognized.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities We reflect all derivative instruments at fair value as either assets or liabilities on the 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 hedging instruments as a component of accumulated other comprehensive income or loss. Any ineffective portion of a derivative’s change in fair value is immediately recognized within net income. For derivatives that do not meet the criteria for hedge accounting, changes in fair value are immediately recognized within net income. See additional discussion in Note 9 Derivatives and Hedging Activities.
Internal-Use Software	Internal-Use Software We recognize internal-use software development costs based on the development stage of the project and nature of the cost. Internal and external costs incurred during the preliminary project stage are expensed as they are incurred. Internal and external costs incurred to develop internal-use software during the application development stage are capitalized. Internal and external training costs and maintenance costs during the post-implementation-operation stage are expensed as incurred. Completed projects are placed into service and amortized over the estimated useful life of the software. For the years ended December 31, 2016, 2015, and 2014, we recorded zero, $0.3 million, and $2.0 million, respectively, related to impairment of internal use software.
Revenue Recognition	Revenue Recognition All customer leases are classified as operating leases and minimum rents are recognized on a straight-line basis over the customer’s lease term. The excess of rents recognized over amounts contractually due pursuant to the underlying leases are included in deferred rent receivable, and included in other assets in the consolidated balance sheets. If a lease terminates prior to its stated expiration, the deferred rent receivable relating to that lease is written off as a reduction of rental revenue. When arrangements include multiple elements, the revenue associated with separate elements is allocated based on the relative fair values of those elements. The revenue associated with each element is then recognized as earned. Interconnection services and additional space services are considered as separate earnings processes that are provided and completed on a month-to-month basis and revenue is recognized in the period that services are performed. Customer set-up charges and utility installation fees are initially deferred and recognized over the term of the lease 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, tenant reimbursements or other billed amounts is considered by management to be uncollectible. At December 31, 2016, and 2015, the allowance for doubtful accounts totaled $0.2 million and $0.1 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 the Black-Scholes option-pricing model. The fair value of restricted share-based and Operating Partnership unit compensation is based on the fair value of our common stock on the date of the grant. The fair value of performance share awards, which have a market condition, is based on a Monte Carlo simulation. The fair value for all share-based compensation is amortized on a straight-line basis over the vesting period.
Asset Retirement and Environmental Remediation Obligations	Asset Retirement and Environmental Remediation Obligations We record accruals for estimated asset retirement and environmental remediation obligations. The obligations relate primarily to the removal of asbestos 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, 2016, and 2015, the amounts included in unearned revenue, prepaid rent and other liabilities on the consolidated balance sheets were approximately $1.4 million and $1.7 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 generally are not subject to corporate level federal income tax on the earnings distributed currently to our stockholders. If we fail to qualify as a REIT in any taxable year, and are unable to avail ourselves of certain savings provisions set forth in the Code, all of our taxable income would be subject to federal income tax at regular corporate rates, including any applicable alternative minimum tax. To maintain REIT status, we must distribute a minimum of 90% of our taxable income. However, it is our policy and intent, subject to change, to distribute 100% of our taxable income and therefore, no provision is required in the accompanying consolidated financial statements for federal income taxes with regards to activities of the REIT and its subsidiary pass‑through entities. The allocable share of taxable income is included in the income tax returns of its stockholders. The Company is subject to the statutory requirements of the locations in which it conducts business. State and local income taxes are accrued as deemed required in the best judgment of management based on analysis and interpretation of respective tax laws. We have elected to treat certain subsidiaries as a TRS. Certain activities that we undertake must be conducted by a TRS, such as services for our tenants that could be considered otherwise impermissible for us to perform and holding assets that we cannot hold directly. A TRS is subject to corporate level federal and state income taxes. Deferred income taxes are recognized in certain taxable entities. Deferred income tax generally is a function of the period’s temporary differences (items that are treated differently for tax purposes than for financial reporting purposes), the utilization of tax net operating losses generated in prior years that previously had been recognized as deferred income tax assets and the reversal of any previously recorded deferred income tax liabilities. A valuation allowance for deferred income tax assets is provided if we believe all or some portion of the deferred income tax asset may more likely than not be 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, 2016, and 2015, the gross deferred income taxes were not material. We currently have no liabilities for uncertain income tax positions. The earliest tax year for which we are subject to examination is 2013.
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 Accoun27

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Schedule of useful lives of real estate investment assets	Buildings 27 to 40 years Building improvements 1 to 10 years Leasehold improvements The shorter of the lease term or useful life of the asset
Schedule of deferred leasing costs, net of amortization	Deferred leasing costs are included within other assets in the consolidated balance sheets and consisted of the following, net of amortization, as of December 31, 2016, and 2015 (in thousands): December 31, December 31, 2016 2015 Internal sales commissions $ $ Third party commissions External legal counsel Total $ $

Acquired Intangible Assets an28

Acquired Intangible Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2016
Acquired Intangible Assets and Liabilities
Schedule of above-market and below-market lease intangibles and other intangibles	Above-market and below-market lease intangibles and other intangibles balances at December 31, 2016, and 2015, are as follows (in thousands): December 31, December 31, 2016 2015 Lease contracts above-market value $ $ Accumulated amortization Lease contracts above-market value, net $ $ Lease contracts below-market value $ $ Accumulated amortization Lease contracts below-market value, net $ $ Other identified intangible assets $ $ Accumulated amortization Other identified intangible assets, net $ $
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, 2017 $ 2018 2019 2020 2021 Thereafter Total $
The estimated amortization of deferred leasing costs for each of the five succeeding fiscal years	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, 2017 $ 2018 2019 2020 2021 Thereafter Total $

Investment in Real Estate (Tabl

Investment in Real Estate (Tables)	12 Months Ended
	Dec. 31, 2016
Investment in Real Estate
Summary of properties owned or leased	The following is a summary of the properties owned or leased by market at December 31, 2016 (in thousands): Buildings and Construction in Market Land Improvements Progress Total Cost Boston $ $ $ $ Chicago Denver — Los Angeles Miami — New York Northern Virginia San Francisco Bay Total $ $ $ $

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2016
Other Assets.
Schedule of other assets	Our other assets consisted of the following, net of amortization and depreciation, if applicable, as of December 31, 2016, and 2015 (in thousands): December 31, December 31, 2016 2015 Deferred leasing costs $ $ Deferred rent receivable Internal-use software Prepaid expenses Corporate furniture, fixtures and equipment Deferred financing costs Other Total $ $
Estimated amortization of deferred leasing costs for each of the five succeeding fiscal years	The estimated amortization of deferred leasing costs for each of the five succeeding fiscal years is as follows (in thousands): Year Ending December 31, 2017 $ 2018 2019 2020 2021 Thereafter Total $

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2016
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, 2016, are as follows (in thousands): Year Ending December 31, 2017 $ 2018 2019 2020 2021 Thereafter Total $
Schedule of future minimum lease payments to be paid under noncancelable leases	The future minimum lease payments to be paid under noncancelable real estate leases in effect at December 31, 2016, are as follows (in thousands): Year Ending December 31, 2017 $ 2018 2019 2020 2021 Thereafter Total $

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt
Summary of outstanding indebtedness	A summary of outstanding indebtedness as of December 31, 2016, and 2015, is as follows (in thousands): Maturity December 31, December 31, Interest Rate Date 2016 2015 Revolving credit facility 2.32% and 1.98% at December 31, 2016, and December 31, 2015, respectively June 24, 2019 $ $ 2019 Senior unsecured term loan (1) 3.23% at December 31, 2016, and December 31, 2015 January 31, 2019 2020 Senior unsecured term loan (2) 2.60% and 2.43% at December 31, 2016, and December 31, 2015 June 24, 2020 2021 Senior unsecured term loan 2.27% at December 31, 2016 February 2, 2021 — 2023 Senior unsecured notes 4.19% at December 31, 2016 June 15, 2023 — Total principal outstanding Unamortized deferred financing costs Total debt $ $ (1) Our Operating Partnership entered into a swap agreement with respect to the 2019 Term Loan (as defined below) to swap the variable interest rate associated with $100 million, or 100%, of the 2019 Term Loan to a fixed rate of approximately 3.23% per annum at our current leverage ratio. See “Derivatives and Hedging Activities” in Note 9 below. (2) Our Operating Partnership entered into a swap agreement with respect to the 2020 Term Loan to swap the variable interest rate associated with $75 million, or 50%, of the principal amount of the 2020 Term Loan (as defined below) to a fixed rate of approximately 2.93% per annum at our current leverage ratio. The interest rate on the remaining $75 million of the 2020 Term Loan is based on LIBOR plus the applicable spread. The effective interest rate as of December 31, 2016, is 2.60%. See “Derivatives and Hedging Activities” in Note 9 below.
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 and when such debt currently becomes due (in thousands): Year Ending December 31, 2017 $ — 2018 — 2019 2020 2021 Thereafter Total principal outstanding Unamortized deferred financing costs Total debt, net $

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity
Schedule of dividends paid per share on Series A Cumulative Preferred Stock and common shares	Year Ended December 31, Record Date 2016 2015 2014 Common Stock: Ordinary income $ $ $ Qualified dividend — — — Capital gains — — — Return of capital — — — Total dividend (1) $ $ $ Preferred Stock: Ordinary income $ $ $ Qualified dividend — — — Capital gains — — — Total dividend (2) $ $ $ (1) Of the $2.36 taxable dividend in 2016, $0.80 was paid in January 2017, of which $0.44 will apply to tax year 2017. Of the $1.70 taxable dividend in 2015, $0.53 was paid in January 2016, of which $0.41 will apply to tax year 2016. Of the $1.15 taxable dividends in 2014, $0.42 was paid in January 2015, of which $0.32 applies to tax year 2015. (2) Of the $1.81 taxable dividend in 2016, $0.45 was paid in January 2017. Of the $1.81 taxable dividend in 2015, $0.45 was paid in January 2016. Of the $1.81 taxable dividend in 2014, $0.45 was paid in January 2015.

Noncontrolling Interests - Op34

Noncontrolling Interests - Operating Partnership (Tables)	12 Months Ended
	Dec. 31, 2016
Noncontrolling Interests - Operating Partnership
Schedule of ownership interests in our Operating Partnership	December 31, 2016 December 31, 2015 Number of Units Percentage of Total Number of Units Percentage of Total CoreSite Realty Corporation % % Noncontrolling interests Total % %

Equity Incentive Award Plan (Ta

Equity Incentive Award Plan (Tables)	12 Months Ended
	Dec. 31, 2016
Equity Incentive Award Plan
Schedule of stock option activity	Number of Weighted Weighted Aggregate Options outstanding, December 31, 2013 $ 7.6 years $14.0 million Granted — — Exercised $5.6 million Forfeited Expired Options outstanding, December 31, 2014 $ 6.7 years $13.7 million Granted — — Exercised $12.0 million Forfeited Expired Options outstanding, December 31, 2015 $ 5.8 years $11.9 million Granted — — Exercised $3.8 million Forfeited — — Expired — — Options outstanding, December 31, 2016 $ 5.0 years $15.0 million Exercisable at December 31, 2014 $ 6.4 years $9.6 million 2015 $ 5.4 years $9.0 million 2016 $ 4.9 years $14.2 million
Schedule of unvested shares subject to options	Number of Weighted Unvested balance, December 31, 2013 $ Granted — — Forfeited Vested Unvested balance, December 31, 2014 $ Granted — — Forfeited Vested Unvested balance, December 31, 2015 $ Granted — — Forfeited — — Vested Unvested balance, December 31, 2016 $
Schedule of restricted awards and RSUs	Restricted Weighted Unvested balance, December 31, 2013 $ Granted Forfeited Vested Unvested balance, December 31, 2014 $ Granted Forfeited Vested Unvested balance, December 31, 2015 $ Granted Forfeited Vested Unvested balance, December 31, 2016 $
Schedule of unvested PSAs and their weighted-average fair value at the date of grant	Weighted- Average Fair Performance-Based Restricted Stock Awards Value at Grant Minimum Maximum Target Date Unvested balance, December 31, 2013 — — — $ — Granted — Performance adjustment — — — — Forfeited — Vested — — — Unvested balance, December 31, 2014 — $ Granted Performance adjustment — Forfeited Vested Unvested balance, December 31, 2015 $ Granted Performance adjustment — — Forfeited Vested Unvested balance, December 31, 2016 $
Summary of assumptions used to value performance stock awards	2016 2015 2014 Expected term (in years) Expected volatility % % % Expected annual dividend(1) — — — Risk-free rate % % % ______________________ (1) The fair value of the PSAs assumes reinvestment of dividends.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share
Summary of basic and diluted income per share	The following is a summary of basic and diluted net income per share (in thousands, except share and per share amounts): Year Ended December 31, 2016 2015 2014 Net income attributable to common shares $ $ $ Weighted-average common shares outstanding - basic Effect of potentially dilutive common shares: Stock options Unvested awards Weighted-average common shares outstanding - diluted Net income per share attributable to common shares Basic $ $ $ Diluted $ $ $

Quarterly Financial Informati37

Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information (unaudited)
Schedule of selected quarterly information	The table below reflects the selected quarterly information for the years ended December 31, 2016, and 2015 (in thousands except share data): Three Months Ended December 31, September 30, June 30, March 31, 2016 2016 2016 2016 Revenue $ $ $ $ Operating income Net income Net income attributable to common shares Net income per share attributable to common shares - basic $ $ $ $ Net income per share attributable to common shares - diluted $ $ $ $ Three Months Ended December 31, September 30, June 30, March 31, 2015 2015 2015 2015 Revenue $ $ $ $ Operating income Net income Net income attributable to common shares Net income per share attributable to common shares - basic $ $ $ $ Net income per share attributable to common shares - diluted $ $ $ $

Organization (Details)

Organization (Details) - Operating partnership	Dec. 31, 2016
Organization
Percentage of ownership interests held by the entity	70.70%
Percentage of ownership interests held by others	29.30%

Summary of Significant Accoun39

Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Minimum
Recent Accounting Pronouncements
Right of use liability	$ 100
Right of use asset	100
Lease costs in sales and marketing expense	1
Maximum
Recent Accounting Pronouncements
Right of use liability	300
Right of use asset	300
Estimated increase in straight-line rental expense	6
Lease costs in sales and marketing expense	$ 2

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Real Estate (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments in Real Estate
Capitalized interest costs	$ 4.1	$ 3.7	$ 4.6
Depreciation expense	$ 89.2	$ 76.1	$ 65.1
Building | Minimum
Investments in Real Estate
Useful lives	27 years
Building | Maximum
Investments in Real Estate
Useful lives	40 years
Building Improvements | Minimum
Investments in Real Estate
Useful lives	1 year
Building Improvements | Maximum
Investments in Real Estate
Useful lives	10 years

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Deferred Costs & Impairment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of Significant Accounting Policies
Impairment loss related to intangible assets	$ 0	$ 0	$ 0
Goodwill	41,191,000	41,191,000
Impairment loss related to goodwill	0	0	0
Deferred Costs
Internal sales commissions	18,748,000	17,558,000
Third party commissions	13,643,000	15,866,000
External legal counsel	730,000	718,000
Total	33,121,000	34,142,000
Recoverability of Long-Lived Assets
Impairment of real estate	$ 0	$ 0	$ 0

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Internal Use Software, RR & IT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Internal-Use Software
Recognized impairment of internal use software	$ 0	$ 300	$ 2,000
Revenue Recognition
Increase to rental revenue	500	500	$ 600
Allowance for doubtful accounts (in dollars)	209	56
Asset Retirement and Environmental Remediation Obligations
Asset retirement and environmental remediation obligations	$ 1,400	$ 1,700
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 Accoun43

Summary of Significant Accounting Policies - Concentration of Credit Risks & Segment Information (Details)	12 Months Ended
	Dec. 31, 2016item
Summary of Significant Accounting Policies
Number of off-balance-sheet concentrations of credit risk	0
Segment information
Number of reportable segments	1

Acquisitions (Details)

Acquisitions (Details) $ in Millions	Nov. 10, 2016USD ($)aft²
Acquisitions
Purchase price | $	$ 65
Area of land acquired | a	21.75
Net rentable space | ft²	611,000

Acquired Intangible Assets an45

Acquired Intangible Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Acquired Intangible Assets and Liabilities
New intangible assets added	$ 7,500
New intangible liabilities added	$ 400
Weighted average life of intangible assets	4 years 3 months 18 days
Weighted average life of intangible liabilities	5 years 8 months 12 days
Lease contracts above-market value	$ 2,080	$ 2,191
Accumulated amortization	(1,698)	(1,756)
Lease contracts above-market value, net	382	435
Lease contracts below-market value	9,731	9,972
Accumulated amortization	(5,439)	(5,279)
Lease contracts below-market value, net	4,292	4,693
Other identified intangible assets	20,218	13,960
Accumulated amortization	(10,687)	(9,681)
Other identified intangible assets, net	9,531	4,279
Amortization of above and below Market Leases	500	500	$ 600
Accumulated amortization of below-market lease	5,439	5,279
Estimated amortization of acquired below-market leases, net of acquired above-market leases
2,017	600
2,018	603
2,019	280
2,020	175
2,021	168
Thereafter	2,084
Total	3,910
Estimated amortization of all other identified intangible assets
2,017	3,410
2,018	2,028
2,019	1,509
2,020	851
2,021	807
Thereafter	926
Total	9,531
Other Intangible Assets [Member]
Acquired Intangible Assets and Liabilities
Amortization of intangible assets	$ 2,000	$ 2,000	$ 3,400

Investment in Real Estate (Deta

Investment in Real Estate (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2016USD ($)	Nov. 10, 2016a	Nov. 30, 2014ft²
Investment in Real Estate
Land	$ 74,819		$ 100,258
Buildings and Improvements	1,037,127		1,472,580
Construction in progress	183,189		70,738
Total investments in real estate			1,643,576
Gain (loss) on real estate disposal	$ 36	$ 1,208
Area of land disposed of in sale | a				21.75
Boston
Investment in Real Estate
Land			5,154
Buildings and Improvements			96,470
Construction in progress			167
Total investments in real estate			101,791
Chicago
Investment in Real Estate
Land			5,493
Buildings and Improvements			98,872
Construction in progress			6,877
Total investments in real estate			111,242
Denver
Investment in Real Estate
Buildings and Improvements			5,377
Construction in progress			5,955
Total investments in real estate			11,332
Los Angeles
Investment in Real Estate
Land			28,467
Buildings and Improvements			235,073
Construction in progress			5,987
Total investments in real estate			269,527
Miami
Investment in Real Estate
Land			728
Buildings and Improvements			10,499
Total investments in real estate			11,227
New York
Investment in Real Estate
Land			2,388
Buildings and Improvements			128,078
Construction in progress			38,632
Total investments in real estate			169,098
Northern Virginia
Investment in Real Estate
Land			26,642
Buildings and Improvements			292,173
Construction in progress			12,085
Total investments in real estate			330,900
San Francisco Bay
Investment in Real Estate
Land			31,386
Buildings and Improvements			606,038
Construction in progress			1,035
Total investments in real estate			$ 638,459
BO1 Somerville MA
Investment in Real Estate
Gain (loss) on real estate disposal		$ 1,200
Area of land disposed of in sale | ft²					52,248

Other Assets (Details)

Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Other Assets.
Deferred leasing costs	$ 33,121	$ 34,142
Deferred rent receivable	36,393	29,309
Internal-use software	14,440	10,467
Prepaid expense	4,390	2,689
Corporate furniture, fixtures and equipment	5,356	6,157
Deferred financing costs	1,604	2,251
Other	1,068	1,618
Total	96,372	86,633
Estimated amortization of deferred leasing costs
2,017	14,066
2,018	9,644
2,019	4,190
2,020	1,672
2,021	1,303
Thereafter	2,246
Total	$ 33,121	$ 34,142

Leases (Detail)

Leases (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Future minimum lease payments to be received under noncancelable leases
2,017	$ 222,932
2,018	166,859
2,019	116,940
2,020	84,493
2,021	71,929
Thereafter	196,737
Total	859,890
Operating leases
2,017	20,485
2,018	20,849
2,019	21,515
2,020	21,923
2,021	21,638
Thereafter	19,784
Total	$ 126,194

Debt - Summary of Debt (Details

Debt - Summary of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Jun. 15, 2016	Dec. 31, 2015	Apr. 09, 2015	Feb. 03, 2014
Debt
Interest rate as of reporting date (as a percent)				2.93%	3.23%
Total principal outstanding	$ 694,000		$ 392,250
Unamortized deferred financing costs	(3,550)		(1,243)
Total debt	$ 690,450		$ 391,007
Revolving Credit Facility
Debt
Interest rate as of reporting date (as a percent)	2.32%		1.98%
Debt	$ 194,000		$ 142,250
2019 Senior Unsecured Term Loan
Debt
Interest rate as of reporting date (as a percent)	3.23%		3.23%
Debt	$ 100,000		$ 100,000
2020 Senior Unsecured Term Loan
Debt
Interest rate as of reporting date (as a percent)	2.60%		2.43%
Debt	$ 150,000		$ 150,000
2020 Senior Unsecured Term Loan | Senior Unsecured Term Loan
Debt
Amount borrowed under term loan or revolving credit facility	$ 75,000
2021 Senior Unsecured Term Loan
Debt
Interest rate as of reporting date (as a percent)	2.27%
Total principal outstanding	$ 100,000
2023 Senior Unsecured Term Loan
Debt
Interest rate as of reporting date (as a percent)	4.19%
Total principal outstanding	$ 150,000
Amount borrowed under term loan or revolving credit facility		$ 150,000
Operating partnership | 2019 Senior Unsecured Term Loan | Interest Rate Swap
Debt
Percentage of debt hedged	100.00%
Operating partnership | 2020 Senior Unsecured Term Loan | Interest Rate Swap
Debt
Interest rate as of reporting date (as a percent)	2.93%
Amount borrowed under term loan or revolving credit facility	$ 75,000
Percentage of debt hedged	50.00%

Debt - Revolving Credit Facilit

Debt - Revolving Credit Facility (Details) $ in Millions	Feb. 02, 2016USD ($)	Jun. 24, 2015USD ($)item	Dec. 31, 2016USD ($)
Revolving Credit Facility
Debt
Maximum borrowing capacity			$ 350
Borrowed and outstanding			194
Letters of credit outstanding			4.5
Amount available for borrowing under the facility			$ 151.5
Leverage ratio (as a percent)			0.00%
Revolving Credit Facility | LIBOR
Debt
Interest rate margin (as a percent)			1.55%
Reference rate			LIBOR
Revolving Credit Facility | LIBOR | Minimum
Debt
Interest rate margin (as a percent)			1.55%
Revolving Credit Facility | LIBOR | Maximum
Debt
Interest rate margin (as a percent)			2.25%
Revolving Credit Facility | Base Rate
Debt
Reference rate			base rate
Revolving Credit Facility | Base Rate | Minimum
Debt
Interest rate margin (as a percent)			0.55%
Revolving Credit Facility | Base Rate | Maximum
Debt
Interest rate margin (as a percent)			1.25%
Credit Agreement
Debt
Number of options available for extensions | item		1
Extension fee (as a percent)		0.10%
Total increase in commitment under accordion feature	$ 100
Maximum borrowing capacity	600	$ 500
Maximum borrowing capacity including accordion feature	$ 800	700
Leverage ratio, Covenant (as a percent)			60.00%
Leverage ratio (as a percent)			23.30%
Secured debt ratio, Covenant (as a percent)			40.00%
Secured debt ratio (as a percent)			0.00%
Fixed charge coverage ratio			8
Unhedged variable rate debt ratio, Covenant (as a percent)			30.00%
Unhedged variable rate debt ratio (as a percent)			12.30%
Credit Agreement | Minimum
Debt
Fixed charge coverage ratio, Covenant			1.7
Credit Agreement | Revolving Credit Facility
Debt
Maximum borrowing capacity		350
Credit Agreement | Senior Unsecured Term Loan
Debt
Unsecured term loan		$ 150

Debt - Unsecured Debt (Details)

Debt - Unsecured Debt (Details) - USD ($) $ in Millions	Feb. 02, 2016	Jun. 24, 2015	Jan. 31, 2014	Dec. 31, 2016	Jun. 15, 2016
2019 Senior Unsecured Term Loan
Debt
Unsecured term loan			$ 100
Term of loan facility			5 years
Increase in accordion feature borrowing capacity			$ 100
Accordion feature			$ 200
Leverage ratio (as a percent)				23.30%
2019 Senior Unsecured Term Loan | LIBOR
Debt
Reference rate				LIBOR
Interest rate margin (as a percent)				1.75%
2019 Senior Unsecured Term Loan | LIBOR | Minimum
Debt
Interest rate margin (as a percent)				1.75%
2019 Senior Unsecured Term Loan | LIBOR | Maximum
Debt
Interest rate margin (as a percent)				2.65%
2019 Senior Unsecured Term Loan | Base Rate
Debt
Reference rate				base rate
2019 Senior Unsecured Term Loan | Base Rate | Minimum
Debt
Interest rate margin (as a percent)				0.75%
2019 Senior Unsecured Term Loan | Base Rate | Maximum
Debt
Interest rate margin (as a percent)				1.65%
2020 Senior Unsecured Term Loan
Debt
Unsecured term loan		$ 150
Term of loan facility		5 years
Leverage ratio (as a percent)				23.30%
2020 Senior Unsecured Term Loan | LIBOR
Debt
Reference rate				LIBOR
Interest rate margin (as a percent)				1.50%
2020 Senior Unsecured Term Loan | LIBOR | Minimum
Debt
Interest rate margin (as a percent)				1.50%
2020 Senior Unsecured Term Loan | LIBOR | Maximum
Debt
Interest rate margin (as a percent)				2.20%
2020 Senior Unsecured Term Loan | Base Rate
Debt
Reference rate				base rate
2020 Senior Unsecured Term Loan | Base Rate | Minimum
Debt
Interest rate margin (as a percent)				0.50%
2020 Senior Unsecured Term Loan | Base Rate | Maximum
Debt
Interest rate margin (as a percent)				1.20%
2020 Senior Unsecured Term Loan | Senior Unsecured Term Loan
Debt
Aggregate principal amount				$ 75
2021 Senior Unsecured Term Loan
Debt
Unsecured term loan	$ 100
Term of loan facility	5 years
Leverage ratio (as a percent)				23.30%
2021 Senior Unsecured Term Loan | LIBOR
Debt
Reference rate				LIBOR
Interest rate margin (as a percent)				1.50%
2021 Senior Unsecured Term Loan | LIBOR | Minimum
Debt
Interest rate margin (as a percent)				1.50%
2021 Senior Unsecured Term Loan | LIBOR | Maximum
Debt
Interest rate margin (as a percent)				2.20%
2021 Senior Unsecured Term Loan | Base Rate
Debt
Reference rate				base rate
2021 Senior Unsecured Term Loan | Base Rate | Minimum
Debt
Interest rate margin (as a percent)				0.50%
2021 Senior Unsecured Term Loan | Base Rate | Maximum
Debt
Interest rate margin (as a percent)				1.20%
2023 Senior Unsecured Term Loan
Debt
Aggregate principal amount					$ 150
Stated interest rate					4.19%
Percentage of term notes that may be prepaid					100.00%
Percentage of term notes that holders have right to purchase in cash					100.00%
Percentage of term notes that holders may redeem for cash					100.00%

Debt - Maturities (Details)

Debt - Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Debt maturities
2,019	$ 294,000
2,020	150,000
2,021	100,000
Thereafter	150,000
Total principal outstanding	694,000	$ 392,250
Unamortized deferred financing costs	(3,550)	(1,243)
Total debt	$ 690,450	$ 391,007

Derivatives and Hedging Activ53

Derivatives and Hedging Activities (Details) - USD ($) $ in Thousands	Jan. 01, 2017	Apr. 09, 2015	Feb. 03, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative instruments and hedging activities disclosures
Amount of gain (loss) recorded in accumulated other comprehensive income				$ (1,112)	$ (2,426)	$ (1,409)
Cash Flow Hedging
Derivative instruments and hedging activities disclosures
Earnings related to derivatives due to hedge ineffectiveness				0	0	0
Interest Rate Swap | Designated as Hedging Instrument | Cash Flow Hedging
Derivative instruments and hedging activities disclosures
Amount borrowed under term loan or revolving credit facility		$ 75,000	$ 100,000
Term of loan facility		5 years	5 years
Derivative, Fixed Interest Rate		2.93%	3.23%
Amount of gain (loss) recorded in accumulated other comprehensive income				1,100	2,400	1,400
Amount reclassified to interest expense				1,700	1,900	$ 1,100
Amount recognized in unearned revenue, prepaid rent and other liabilities				400	800
Derivative asset recognized in other assets				$ 300	$ 0
Interest Rate Swap | Designated as Hedging Instrument | Cash Flow Hedging | Forecast
Derivative instruments and hedging activities disclosures
Amount estimated to be reclassified as an increase to interest expense	$ 900
LIBOR | Interest Rate Swap | Designated as Hedging Instrument | Cash Flow Hedging
Derivative instruments and hedging activities disclosures
Reference rate		one-month LIBOR

Stockholders' Equity (Details)

Stockholders' Equity (Details)	Dec. 12, 2012USD ($)$ / sharesshares	Dec. 31, 2016USD ($)item$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)
Stockholders' Equity
Stock authorized to be issued (in shares)		120,000,000
Common stock, shares authorized		100,000,000	100,000,000
Preferred stock authorized to be issued (in shares)		20,000,000
Common Stock, shares issued		33,896,771	30,650,703
Common Stock, shares outstanding		33,896,771	30,650,703
Number of Operating Partnership Units (in shares)		47,227,915	46,994,903
Series A Cumulative Preferred Stock, shares issued		4,600,000	4,600,000
Proceeds from exercise of stock options | $		$ 1,290,000	$ 1,393,000	$ 2,354,000
Series A Cumulative Preferred Stock, dividend rate (as a percent)		7.25%	7.25%
Series A Cumulative Preferred Stock, liquidation preference (in dollars per share) | $ / shares		$ 25	$ 25
2010 Plan
Stockholders' Equity
Amount of shares of common stock issued under the plan | $		$ 239,068	$ 393,337	370,214
Proceeds from exercise of stock options | $		$ 1,300,000		$ 900,000
Payments made for exercise of stock options | $			$ (2,900,000)
Operating partnership
Stockholders' Equity
Common Operating Partnership units redeemed for common stock (in shares)		3,007,000	8,500,000
Redemption of noncontrolling interests (in shares)		3,007,000	8,500,000
Series A Cumulative Preferred Stock, dividend rate (as a percent)	7.25%
Series A Cumulative Redeemable Preferred Stock
Stockholders' Equity
Series A Cumulative Preferred Stock, shares issued	4,600,000
Net Proceeds from issuance of preferred stock | $	$ 110,600,000
Cumulative dividends each year on preferred stock (in dollars per share) | $ / shares	$ 1.8125
Redemption price of preferred stock (in dollars per share) | $ / shares		$ 25
Minimum number of quarters in which no payment of preferred stock dividends leads to entitlement of voting rights | item		6
Conversion ratio of preferred stock		1.944
Series A Cumulative Preferred Stock, dividend rate (as a percent)	7.25%
Series A Cumulative Preferred Stock, liquidation preference (in dollars per share) | $ / shares	$ 25

Stockholders' Equity - Dividend

Stockholders' Equity - Dividends (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015	Dec. 31, 2014
Minimum
Dividends
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%
Common Stock
Dividends
Ordinary income (in dollars per share)		$ 2.36	$ 1.70				$ 1.15
Total dividend (in dollars per share)		2.36	1.70				1.15
Dividend declared taxable	$ 0.44	0.41	0.32
Ordinary dividend paid (in dollars per share)				$ 0.80	$ 0.53	$ 0.42
Preferred Stock
Dividends
Ordinary income (in dollars per share)		1.81	1.81				1.81
Total dividend (in dollars per share)		$ 1.81	$ 1.81				$ 1.81
Ordinary dividend paid (in dollars per share)				$ 0.45	$ 0.45	$ 0.45

Noncontrolling Interests - Op56

Noncontrolling Interests - Operating Partnership (Details) $ / shares in Units, $ in Thousands	Dec. 30, 2016$ / shares	Dec. 12, 2012shares	Sep. 30, 2016$ / shares	Jun. 30, 2016$ / shares	Mar. 31, 2016$ / shares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)shares
Noncontrolling Interests - Operating Partnership
Conversion ratio for common operating partnership units						1
Series A Cumulative Preferred Stock, dividend rate (as a percent)						7.25%	7.25%
Number of Operating Partnership Units (in shares)						47,227,915	46,994,903
Percentage of Total						100.00%	100.00%
Shares of common stock issued related to employee compensation arrangements						233,012
Coresite Realty Corporation
Noncontrolling Interests - Operating Partnership
Number of Operating Partnership Units (in shares)						33,376,568	30,136,556
Percentage of Total						70.70%	64.10%
Noncontrolling Interests
Noncontrolling Interests - Operating Partnership
Number of Operating Partnership Units (in shares)						13,851,347	16,858,347
Percentage of Total						29.30%	35.90%
Reduction to noncontrolling interests in the Operating Partnership and an increase to common stock and additional paid in capital | $						$ 37,374	$ 110,180
Operating partnership
Noncontrolling Interests - Operating Partnership
Preferred Operating Partnership units issued to CoreSite Realty Corporation (in shares)		4,600,000
Series A Cumulative Preferred Stock, dividend rate (as a percent)		7.25%
Percentage of Total						70.70%
Percentage of Total						29.30%
Quarterly distributions will receive by holders of operating partnership units (in dollars per unit) | $ / shares	$ 0.80		$ 0.53	$ 0.53	$ 0.53
Common Operating Partnership units redeemed for common stock (in shares)						3,007,000	8,500,000
Redemption of noncontrolling interests (in shares)						3,007,000	8,500,000
Reduction to noncontrolling interests in the Operating Partnership and an increase to common stock and additional paid in capital | $						$ 37,400	$ 110,200
Operating partnership | Noncontrolling Interests
Noncontrolling Interests - Operating Partnership
Redemption value of the noncontrolling interests | $						$ 1,100,000
Closing price of the Company's stock (in dollars per share) | $ / shares						$ 79.37

Equity Incentive Award Plan (De

Equity Incentive Award Plan (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity Incentive Plan
Shares of common stock reserved for issuance	6,000,000
Shares of common stock that were available for issuance	3,109,189
Stock Options
Number of Shares Subject to Option
Options outstanding at the beginning of the period (in shares)	340,210	758,095	1,133,915
Exercised (in shares)	(74,660)	(410,322)	(307,022)
Forfeited (in shares)		(7,281)	(64,851)
Expired (in shares)		(282)	(3,947)
Options outstanding at the end of the period (in shares)	265,550	340,210	758,095	1,133,915
Exercisable at the end of the period (in shares)	249,227	234,943	474,132
Number of Shares Subject to Option
Unvested balance at the beginning of the period (in shares)	105,267	283,964	635,739
Forfeited (in shares)		(7,281)	(64,851)
Vested (in shares)	(88,944)	(171,416)	(286,924)
Unvested balance at the end of the period (in shares)	16,323	105,267	283,964	635,739
Weighted Average Fair Value at Grant
Unvested balance at the beginning of the period (in dollars per share)	$ 9.13	$ 7.75	$ 7.10
Forfeited (in dollars per share)		8.48	8.03
Vested (in dollars per share)	8.97	6.86	6.25
Unvested balance at the end of the period (in dollars per share)	$ 9.99	$ 9.13	$ 7.75	$ 7.10
Compensation cost not yet recognized
Unearned compensation	$ 0.1
Vesting period	2 months 12 days
Weighted Average Remaining Contractual Term
Options outstanding at the end of the period	5 years	5 years 9 months 18 days	6 years 8 months 12 days	7 years 7 months 6 days
Exercisable at the end of the period	4 years 10 months 24 days	5 years 4 months 24 days	6 years 4 months 24 days
Aggregate Intrinsic Value
Exercised	$ 3.8	$ 12	$ 5.6
Outstanding at the end of the period	15	11.9	13.7	$ 14
Exercisable at the end of the period	$ 14.2	$ 9	$ 9.6
Stock Options | Weighted Average
Weighted Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 21.77	$ 20.94	$ 19.89
Exercised (in dollars per share)	17.27	20.15	16.10
Forfeited (in dollars per share)		27.53	25.83
Expired (in dollars per share)		15.23	15.80
Options outstanding at the end of the period (in dollars per share)	22.96	21.77	20.94	$ 19.89
Exercisable at the end of the period (in dollars per share)	$ 22.29	$ 18.47	$ 18.78
Restricted Awards
Restricted Awards and PSA's
Unvested balance at the beginning of the period (in shares)	377,612	394,016	495,151
Granted (in shares)	182,628	187,644	216,175
Forfeited (in shares)	(37,383)	(34,788)	(109,798)
Vested (in shares)	(199,216)	(169,260)	(207,512)
Unvested balance at the end of the period (in shares)	323,641	377,612	394,016	495,151
Weighted Average Fair Value at Grant
Unvested balance at the beginning of the period (in dollars per share)	$ 38.51	$ 29.10	$ 25.08
Granted (in dollars per share)	66.69	47.41	31.51
Forfeited (in dollars per share)	53.87	36.06	27.64
Vested (in dollars per share)	36.57	26.96	22.79
Unvested balance at the end of the period (in dollars per share)	$ 53.84	38.51	29.10	$ 25.08
Compensation cost not yet recognized
Unearned compensation	$ 12.3
Restricted Awards | Weighted Average
Compensation cost not yet recognized
Vesting period	2 years 6 months
PSAs
Weighted Average Fair Value at Grant
Unvested balance at the beginning of the period (in dollars per share)	$ 42.78	25.89
Granted (in dollars per share)	84.78	61.22	25.89
Forfeited (in dollars per share)	69.12	43.38	25.89
Vested (in dollars per share)	42.17	25.89	25.89
Unvested balance at the end of the period (in dollars per share)	$ 54.24	$ 42.78	$ 25.89
Compensation cost not yet recognized
Unearned compensation	$ 2.9
Percentage of awards eligible to be earned upon TSR achievement in year one of the performance period	20.00%
Percentage of awards eligible to be earned upon TSR achievement in year two of the performance period	20.00%
Percentage of awards earned upon TSR achievement in year three of the performance period	20.00%
Percentage of awards eligible to be earned upon cumulative TSR achievement over the three-year performance period	40.00%
Assumptions used to value the stock options granted
Expected term	2 years 9 months 29 days	2 years 9 months 29 days	2 years 9 months 29 days
Expected volatility (as a percent)	25.29%	25.51%	32.98%
Risk-free rate (as a percent)	0.97%	1.02%	0.64%
PSAs | 2010 Plan
Assumptions used to value the stock options granted
Performance period	3 years
PSAs | Weighted Average
Compensation cost not yet recognized
Vesting period	2 years
PSAs | Minimum
Restricted Awards and PSA's
Unvested balance at the beginning of the period (in shares)	19,591
Granted (in shares)	11,796	11,222
Performance adjustment	29,256	9,981
Forfeited (in shares)	(13,474)	(1,018)
Vested (in shares)	(1,894)	(594)
Unvested balance at the end of the period (in shares)	45,275	19,591
PSAs | Minimum | 2010 Plan
Compensation cost not yet recognized
Percentage of target number of shares for PSAs granted in 2014	0.00%
Percentage of target number of shares for PSAs granted in years 2015 and 2016	25.00%
PSAs | Maximum
Restricted Awards and PSA's
Unvested balance at the beginning of the period (in shares)	142,963	85,851
Granted (in shares)	82,572	78,553	91,335
Performance adjustment		(7,190)
Forfeited (in shares)	(55,916)	(13,657)	(5,484)
Vested (in shares)	(1,894)	(594)
Unvested balance at the end of the period (in shares)	167,725	142,963	85,851
PSAs | Maximum | 2010 Plan
Compensation cost not yet recognized
Percentage of target number of shares for PSAs granted in 2014	150.00%
Percentage of target number of shares for PSAs granted in years 2015 and 2016	175.00%
PSAs | Target
Restricted Awards and PSA's
Unvested balance at the beginning of the period (in shares)	91,488	57,233
Granted (in shares)	47,184	44,886	60,889
Performance adjustment	11,893	(1,465)
Forfeited (in shares)	(34,695)	(8,572)	(3,656)
Vested (in shares)	(1,894)	(594)
Unvested balance at the end of the period (in shares)	113,976	91,488	57,233

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share
Net income attributable to common shares	$ 14,895	$ 12,180	$ 12,035	$ 11,261	$ 9,342	$ 6,920	$ 5,538	$ 4,568	$ 50,371	$ 26,368	$ 14,427
Weighted-average common shares outstanding - basic									32,289,414	25,218,500	21,161,614
Effect of potentially dilutive common shares:
Stock options									192,464	302,264	349,533
Unvested awards									250,181	185,804	229,560
Weighted-average common shares outstanding - diluted									32,732,059	25,706,568	21,740,707
Net income per share attributable to common shares
Basic (in dollars per share)	$ 0.45	$ 0.36	$ 0.38	$ 0.37	$ 0.32	$ 0.26	$ 0.23	$ 0.21	$ 1.56	$ 1.05	$ 0.68
Diluted (in dollars per share)	$ 0.44	$ 0.36	$ 0.37	$ 0.37	$ 0.32	$ 0.26	$ 0.22	$ 0.21	$ 1.54	$ 1.03	$ 0.66
Weighted-average potentially dilutive securities excluded in calculation of basic and diluted income (loss) per share									29,618	117,048	180,020

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Benefit Plan
Months of service required in order to participate in plan	1 month
Months of service required in order to receive employer contribution	6 months
Safe harbor contribution as a percentage of employee gross pay (as a percent)	3.00%
Company contributions under certain 401(k) savings plans	$ 0.9	$ 0.8	$ 0.8

Estimated Fair Value of Finan60

Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Estimated Fair Value of Financial Instruments
Total principal outstanding	$ 694,000	$ 392,250
Significant Unobservable Inputs (Level 3)
Estimated Fair Value of Financial Instruments
Fair value of debt	$ 673,000	$ 393,000

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($)	Jul. 23, 2015	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies
Settlement amount		$ 600,000
Other expenses
Percentage of operating partnership units that are disposed in certain taxable transactions (as a percent)		90.00%
Maximum
Commitments and Contingencies
Accrued Litigation Liability			$ 3,100,000
Telecommunications Capacity
Commitments and Contingencies
Open commitments		$ 10,300,000
Construction Contracts
Commitments and Contingencies
Open commitments		18,600,000
Damages Related To Services Rendered
Commitments and Contingencies
Loss Contingency, Damages Sought	$ 802,564
Damages For Loss Of Revenue And Other Costs
Commitments and Contingencies
Alleged losses	$ 70,080,000
Pending Litigation | Minimum
Commitments and Contingencies
Accrued Litigation Liability		600,000
Pending Litigation | Maximum
Commitments and Contingencies
Accrued Litigation Liability		3,100,000
Pending Litigation | Accounts Payable and Accrued Expenses
Commitments and Contingencies
Accrued Litigation Liability		2,900,000
Commonwealth Of Virginia
Commitments and Contingencies
Potential sales and use tax liability, if certain thresholds are not met		7,500,000
Commonwealth Of Virginia | Minimum
Commitments and Contingencies
Estimated sales and use tax liability		0
Commonwealth Of Virginia | Maximum
Commitments and Contingencies
Estimated sales and use tax liability		4,000,000
Commonwealth Of Virginia | Accounts Payable and Accrued Expenses
Commitments and Contingencies
Accrued Litigation Liability		$ 0

Quarterly Financial Informati62

Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information (unaudited)
Revenue	$ 110,508	$ 101,274	$ 96,090	$ 92,480	$ 90,919	$ 86,382	$ 81,336	$ 74,655	$ 400,352	$ 333,292	$ 272,420
Operating income	27,933	22,505	22,558	21,621	19,321	16,751	14,676	13,336	94,617	64,084	44,187
Net income	23,161	19,319	19,835	19,606	17,387	14,530	12,882	12,060	81,921	56,859	40,052
Net income attributable to common shares	$ 14,895	$ 12,180	$ 12,035	$ 11,261	$ 9,342	$ 6,920	$ 5,538	$ 4,568	$ 50,371	$ 26,368	$ 14,427
Net income per share attributable to common shares - basic (in dollars per share)	$ 0.45	$ 0.36	$ 0.38	$ 0.37	$ 0.32	$ 0.26	$ 0.23	$ 0.21	$ 1.56	$ 1.05	$ 0.68
Net income per share attributable to common shares - diluted (in dollars per share)	$ 0.44	$ 0.36	$ 0.37	$ 0.37	$ 0.32	$ 0.26	$ 0.22	$ 0.21	$ 1.54	$ 1.03	$ 0.66

Schedule III Real Estate and 63

Schedule III Real Estate and Accumulated Depreciation - Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Initial Cost
Land	$ 103,889
Building and Improvements	424,905
Costs Capitalized Subsequent to Acquisition	1,114,782
Gross Amount Carried As of Year End
Land	100,258
Building and Improvements	1,543,318
Total	1,643,576	$ 1,295,135	$ 1,146,548	$ 1,048,525
Accumulated Depreciation	369,303	$ 284,219	$ 215,978	$ 155,704
Aggregate cost of the total properties for federal income tax purposes	1,592,600
BO1 Somerville MA
Initial Cost
Land	6,100
Building and Improvements	26,748
Costs Capitalized Subsequent to Acquisition	68,943
Gross Amount Carried As of Year End
Land	5,154
Building and Improvements	96,637
Total	101,791
Accumulated Depreciation	43,636
CH1 Chicago IL
Initial Cost
Land	5,493
Building and Improvements	49,522
Costs Capitalized Subsequent to Acquisition	56,227
Gross Amount Carried As of Year End
Land	5,493
Building and Improvements	105,749
Total	111,242
Accumulated Depreciation	28,918
DC1 Washington DC
Initial Cost
Building and Improvements	4,797
Costs Capitalized Subsequent to Acquisition	3,851
Gross Amount Carried As of Year End
Building and Improvements	8,648
Total	8,648
Accumulated Depreciation	5,237
DE1 Denver CO
Initial Cost
Building and Improvements	37
Costs Capitalized Subsequent to Acquisition	9,972
Gross Amount Carried As of Year End
Building and Improvements	10,009
Total	10,009
Accumulated Depreciation	1,496
DE2 Denver CO
Initial Cost
Building and Improvements	4
Costs Capitalized Subsequent to Acquisition	1,319
Gross Amount Carried As of Year End
Building and Improvements	1,323
Total	1,323
Accumulated Depreciation	797
LA1 Los Angeles CA
Initial Cost
Building and Improvements	41,099
Costs Capitalized Subsequent to Acquisition	33,947
Gross Amount Carried As of Year End
Building and Improvements	75,046
Total	75,046
Accumulated Depreciation	33,584
LA2 Los Angeles CA
Initial Cost
Land	28,467
Building and Improvements	94,114
Costs Capitalized Subsequent to Acquisition	71,900
Gross Amount Carried As of Year End
Land	28,467
Building and Improvements	166,014
Total	194,481
Accumulated Depreciation	42,653
MI1 Miami FL
Initial Cost
Land	728
Building and Improvements	9,325
Costs Capitalized Subsequent to Acquisition	1,174
Gross Amount Carried As of Year End
Land	728
Building and Improvements	10,499
Total	11,227
Accumulated Depreciation	2,771
NY1 New York NY
Initial Cost
Costs Capitalized Subsequent to Acquisition	35,581
Gross Amount Carried As of Year End
Building and Improvements	35,581
Total	35,581
Accumulated Depreciation	19,445
NY2 Secaucus NJ
Initial Cost
Land	4,952
Building and Improvements	18,408
Costs Capitalized Subsequent to Acquisition	110,157
Gross Amount Carried As of Year End
Land	2,388
Building and Improvements	131,129
Total	133,517
Accumulated Depreciation	14,761
SV1 San Jose CA
Initial Cost
Land	6,863
Building and Improvements	91,719
Costs Capitalized Subsequent to Acquisition	39,902
Gross Amount Carried As of Year End
Land	6,863
Building and Improvements	131,621
Total	138,484
Accumulated Depreciation	29,694
SV2 Milpitas CA
Initial Cost
Land	5,086
Building and Improvements	5,046
Costs Capitalized Subsequent to Acquisition	24,127
Gross Amount Carried As of Year End
Land	5,086
Building and Improvements	29,173
Total	34,259
Accumulated Depreciation	17,071
SV3 Santa Clara CA
Initial Cost
Land	4,162
Building and Improvements	3,482
Costs Capitalized Subsequent to Acquisition	47,939
Gross Amount Carried As of Year End
Land	3,972
Building and Improvements	51,611
Total	55,583
Accumulated Depreciation	29,811
SV4 Santa Clara CA
Initial Cost
Land	4,632
Building and Improvements	3,716
Costs Capitalized Subsequent to Acquisition	95,088
Gross Amount Carried As of Year End
Land	4,501
Building and Improvements	98,935
Total	103,436
Accumulated Depreciation	30,159
SV5 Santa Clara CA
Initial Cost
Land	2,572
Costs Capitalized Subsequent to Acquisition	23,613
Gross Amount Carried As of Year End
Land	2,544
Building and Improvements	23,641
Total	26,185
Accumulated Depreciation	1,895
SV6 Santa Clara CA
Initial Cost
Land	4,741
Costs Capitalized Subsequent to Acquisition	36,852
Gross Amount Carried As of Year End
Land	4,825
Building and Improvements	36,768
Total	41,593
Accumulated Depreciation	615
SV7 Santa Clara CA
Initial Cost
Land	3,793
Costs Capitalized Subsequent to Acquisition	235,126
Gross Amount Carried As of Year End
Land	3,595
Building and Improvements	235,324
Total	238,919
Accumulated Depreciation	2,606
VA1 Reston VA
Initial Cost
Land	6,903
Building and Improvements	32,939
Costs Capitalized Subsequent to Acquisition	89,705
Gross Amount Carried As of Year End
Land	6,903
Building and Improvements	122,644
Total	129,547
Accumulated Depreciation	52,542
VA2 Reston VA
Initial Cost
Land	5,197
Costs Capitalized Subsequent to Acquisition	128,169
Gross Amount Carried As of Year End
Land	5,539
Building and Improvements	127,827
Total	133,366
Accumulated Depreciation	11,444
Reston Campus Expansion
Initial Cost
Land	14,200
Building and Improvements	43,949
Costs Capitalized Subsequent to Acquisition	1,190
Gross Amount Carried As of Year End
Land	14,200
Building and Improvements	45,139
Total	59,339
Accumulated Depreciation	$ 168

Schedule III Real Estate and 64

Schedule III Real Estate and Accumulated Depreciation - Rollforwards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property
Balance, beginning of year	$ 1,295,135	$ 1,146,548	$ 1,048,525
Additions - property acquisitions	58,149
Additions - improvements	290,292	148,587	98,969
Deduction - cost of land disposal			(946)
Balance, end of year	1,643,576	1,295,135	1,146,548
Accumulated Depreciation
Balance, beginning of year	284,219	215,978	155,704
Additions, net of disposals	85,084	68,241	60,274
Balance, end of year	$ 369,303	$ 284,219	$ 215,978