Cogent Communications (CCOI) 10-K 23 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	COGENT COMMUNICATIONS HOLDINGS, INC.
Entity Central Index Key	1,158,324
Document Type	10-K
Document Period End Date	Dec. 31, 2017
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			$ 1.7
Entity Common Stock, Shares Outstanding		45,968,237
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 247,011	$ 274,319
Accounts receivable, net of allowance for doubtful accounts of $1,499 and $1,734, respectively	39,096	33,598
Prepaid expenses and other current assets	20,011	19,706
Total current assets	306,118	327,623
Property and equipment:
Property and equipment	1,233,756	1,136,470
Accumulated depreciation and amortization	(852,474)	(774,829)
Total property and equipment, net	381,282	361,641
Deferred tax assets	17,616	42,241
Deposits and other assets ($736 and $128 restricted, respectively)	5,572	6,387
Total assets	710,588	737,892
Current liabilities:
Accounts payable	11,592	11,551
Accrued and other current liabilities	47,947	47,149
Installment payment agreement, current portion, net of discount of $337 and $204, respectively	7,816	2,587
Capital lease obligations, current maturities	7,171	6,626
Total current liabilities	74,526	67,913
Senior secured 2022 notes, net of unamortized debt costs of $1,870 and $2,257, respectively and including premium of $382 and $462, respectively	373,512	373,205
Senior unsecured 2021 notes, net of unamortized debt costs of $2,060 and $2,575, respectively	187,165	186,650
Capital lease obligations, net of current maturities	150,333	135,335
Other long term liabilities	27,596	28,043
Total liabilities	813,132	791,146
Commitments and contingencies
Stockholders' equity:
Common stock, $0.001 par value; 75,000,000 shares authorized; 45,960,799 and 45,478,787 shares issued and outstanding, respectively	46	45
Additional paid-in capital	456,696	442,799
Accumulated other comprehensive income	(4,600)	(17,193)
Accumulated deficit	(554,686)	(478,905)
Total stockholders' deficit	(102,544)	(53,254)
Total liabilities and stockholders' equity	$ 710,588	$ 737,892

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Accounts receivable, allowance for doubtful accounts (in dollars)	$ 1,499	$ 1,734
Deposits and other assets, restricted (in dollars)	736	128
Liabilities and stockholders' equity
Installment payment agreement, discount	$ 337	$ 204
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	45,960,799	45,478,787
Common stock, shares outstanding	45,960,799	45,478,787
Senior secured 2022 notes
Liabilities and stockholders' equity
Unamortized debt costs	$ 1,870	$ 2,257
Unamortized debt premium	382	462
Senior unsecured 2021 notes
Liabilities and stockholders' equity
Unamortized debt costs	$ 2,060	$ 2,575

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Service Revenue
Service revenue	$ 485,175	$ 446,900	$ 404,234
Operating expenses:
Network operations (including $604, $573 and $584 of equity-based compensation expense, respectively), exclusive of amounts shown separately	209,278	194,066	174,510
Selling, general, and administrative (including $12,686, $10,162 and $10,931 of equity-based compensation expense, respectively)	127,915	120,709	113,103
Depreciation and amortization	75,926	75,235	70,527
Total operating expenses	413,119	390,010	358,140
Gains on equipment transactions	3,862	7,739	5,443
Gains on capital lease terminations			11,643
Losses on debt extinguishment and redemption		(587)	(10,144)
Operating income	75,918	64,042	53,036
Interest income and other	3,667	1,021	956
Interest expense	(48,467)	(40,803)	(41,280)
Income before income taxes	31,118	24,260	12,712
Income tax expense	(25,242)	(9,331)	(7,816)
Net income	5,876	14,929	4,896
Comprehensive income (loss):
Net income	5,876	14,929	4,896
Foreign currency translation adjustment	12,593	(2,500)	(8,231)
Comprehensive income (loss)	$ 18,469	$ 12,429	$ (3,335)
Net income per common share:
Basic net income per common share (in dollars per share)	$ 0.13	$ 0.33	$ 0.11
Diluted net income per common share (in dollars per share)	0.13	0.33	0.11
Dividends declared per common share (in dollars per share)	$ 1.80	$ 1.51	$ 1.46
Weighted-average common shares - basic (in shares)	44,855,263	44,641,805	44,888,723
Weighted-average common shares - diluted (in shares)	45,184,203	44,873,030	45,159,489

CONSOLIDATED STATEMENTS OF COM5

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Network operations, equity-based compensation expense	$ 604	$ 573	$ 584
Selling, general, and administrative, equity-based compensation expense	$ 12,686	$ 10,162	$ 10,931

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Common stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Balance at Dec. 31, 2014	$ 46	$ 460,576	$ (6,462)	$ (370,366)	$ 83,794
Balance (in shares) at Dec. 31, 2014	46,398,729
Increase (Decrease) in Stockholders' Equity
Forfeitures of shares granted to employees (in shares)	(47,705)
Equity-based compensation		12,554			12,554
Foreign currency translation			(8,231)		(8,231)
Issuances of common stock (in shares)	62,900
Exercises of options		423			423
Exercises of options (in shares)	27,676
Common stock purchases and retirement	$ (1)	(39,394)			(39,395)
Common stock purchases and retirement (in shares)	(1,242,882)
Excess income tax benefit		2			2
Dividends paid				(66,314)	(66,314)
Net income (loss)				4,896	4,896
Balance at Dec. 31, 2015	$ 45	434,161	(14,693)	(431,784)	(12,271)
Balance (in shares) at Dec. 31, 2015	45,198,718
Increase (Decrease) in Stockholders' Equity
Cumulative-effect adjustment from adoption of ASU 2017-09				6,160	6,160
Forfeitures of shares granted to employees (in shares)	(3,824)
Equity-based compensation		11,910			11,910
Foreign currency translation			(2,500)		(2,500)
Issuances of common stock (in shares)	358,130
Exercises of options		1,220			1,220
Exercises of options (in shares)	53,245
Common stock purchases and retirement		(4,492)			(4,492)
Common stock purchases and retirement (in shares)	(127,482)
Dividends paid				(68,210)	(68,210)
Net income (loss)				14,929	14,929
Balance at Dec. 31, 2016	$ 45	442,799	(17,193)	(478,905)	$ (53,254)
Balance (in shares) at Dec. 31, 2016	45,478,787				45,478,787
Increase (Decrease) in Stockholders' Equity
Forfeitures of shares granted to employees (in shares)	(10,181)
Equity-based compensation		14,504			$ 14,504
Foreign currency translation			12,593		12,593
Issuances of common stock	$ 1				1
Issuances of common stock (in shares)	499,654
Exercises of options		1,222			1,222
Exercises of options (in shares)	39,289
Common stock purchases and retirement		(1,829)			(1,829)
Common stock purchases and retirement (in shares)	(46,750)
Dividends paid				(81,657)	(81,657)
Net income (loss)				5,876	5,876
Balance at Dec. 31, 2017	$ 46	$ 456,696	$ (4,600)	$ (554,686)	$ (102,544)
Balance (in shares) at Dec. 31, 2017	45,960,799				45,960,799

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 5,876	$ 14,929	$ 4,896
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	75,926	75,235	70,527
Amortization of debt discount and premium	1,239	1,105	171
Equity-based compensation expense (net of amounts capitalized)	13,290	10,735	11,515
Losses on debt extinguishment and redemption		587	10,144
Gains on capital lease terminations			(11,643)
Gains - equipment transactions and other, net	(4,833)	(7,674)	(4,866)
Deferred income taxes	24,679	9,224	7,709
Changes in operating assets and liabilities:
Accounts receivable	(4,161)	(3,183)	1,119
Prepaid expenses and other current assets	1,146	(2,923)	(2,898)
Deposits and other assets	1,111	(336)	(221)
Accounts payable, accrued liabilities and other long-term liabilities	(2,571)	10,268	(2,644)
Net cash provided by operating activities	111,702	107,967	83,809
Cash flows from investing activities:
Purchases of property and equipment	(45,801)	(45,234)	(35,582)
Proceeds from asset sales			111
Net cash used in investing activities	(45,801)	(45,234)	(35,471)
Cash flows from financing activities:
Net proceeds from issuance of 2022 secured notes--net of debt costs of $1,202 and $1,397, respectively		124,267	248,603
Extinguishment of 2021 unsecured notes		(10,775)
Redemption of 2018 secured notes			(251,280)
Dividends paid	(81,657)	(68,210)	(66,314)
Principal payments of capital lease obligations	(11,201)	(12,466)	(20,215)
Principal payments on installment payment agreement	(3,802)	(21,203)	(670)
Purchases of common stock	(1,829)	(4,492)	(39,394)
Proceeds from exercises of common stock options	1,222	1,220	423
Net cash (used in) provided by financing activities	(97,267)	8,341	(128,847)
Effect of exchange rate changes on cash	4,058	(346)	(3,690)
Net (decrease) increase in cash and cash equivalents	(27,308)	70,728	(84,199)
Cash and cash equivalents, beginning of year	274,319	203,591	287,790
Cash and cash equivalents, end of year	247,011	274,319	203,591
Supplemental disclosures of cash flow information:
Cash paid for interest	47,032	37,125	44,383
Cash paid for income taxes	441	143	577
Non-cash investing and financing activities:
Capital lease obligations incurred	22,595	18,439	25,794
PP&E obtained for installment payment agreement	9,027	5,521	21,873
Fair value of equipment acquired in leases		2,110	595
Non-cash component of network equipment obtained in exchange transactions	$ 3,861	$ 7,739	$ 8,156

CONSOLIDATED STATEMENTS OF CAS8

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Senior secured 2022 notes
Debt costs	$ 1,202	$ 1,397

Description of the business and

Description of the business and summary of significant accounting policies:	12 Months Ended
	Dec. 31, 2017
Description of the business and summary of significant accounting policies:
Description of the business and summary of significant accounting policies:	1. Description of the business and summary of significant accounting policies: Reorganization and merger On May 15, 2014, pursuant to the Agreement and Plan of Reorganization (the "Merger Agreement") by and among Cogent Communications Group, Inc. ("Group"), a Delaware corporation, Cogent Communications Holdings, Inc., a Delaware corporation ("Holdings") and Cogent Communications Merger Sub, Inc., a Delaware corporation, Group adopted a new holding company organizational structure whereby Group is now a wholly owned subsidiary of Holdings. Holdings is a "successor issuer" to Group pursuant to Rule 12g-3(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"). References to the "Company" for events that occurred prior to May 15, 2014 refer to Cogent Communications Group, Inc. and its subsidiaries and on and after May 15, 2014 the "Company" refers to Cogent Communications Holdings, Inc. and its subsidiaries. Description of business The Company is a Delaware corporation and is headquartered in Washington, DC. The Company is a facilities-based provider of low-cost, high-speed Internet access and Internet Protocol ("IP") communications services. The Company's network is specifically designed and optimized to transmit data using IP. The Company delivers its services primarily to small and medium-sized businesses, communications service providers and other bandwidth-intensive organizations in North America, Europe and Asia. The Company offers on-net Internet access services exclusively through its own facilities, which run from its network to its customers' premises. The Company is not dependent on local telephone companies to serve its customers for its on-net Internet access services because of its integrated network architecture. The Company offers its on-net services to customers located in buildings that are physically connected to its network. The Company's on-net service consists of high-speed Internet access and IP connectivity ranging from 100 Megabits per second to 100 Gigabits per second of bandwidth. The Company provides its on-net Internet access services to its corporate and net-centric customers. The Company's corporate customers are located in multi-tenant office buildings and typically include law firms, financial services firms, advertising and marketing firms and other professional services businesses. The Company's net-centric customers include bandwidth-intensive users such as other Internet service providers, telephone companies, cable television companies, web hosting companies, content delivery network companies and commercial content and application service providers. These net-centric customers obtain the Company's services in colocation facilities and in the Company's data centers. The Company operates data centers throughout North America and Europe that allow its customers to collocate their equipment and access the Company's network. In addition to providing its on-net services, the Company provides Internet connectivity to customers that are not located in buildings directly connected to its network. The Company provides this off-net service primarily to corporate customers using other carriers' facilities to provide the "last mile" portion of the link from the customers' premises to the Company's network. The Company also provides certain non-core services that resulted from acquisitions. The Company continues to support but does not actively sell these non-core services. Principles of consolidation The consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles and include the accounts of the Company and all of its wholly-owned and majority-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Use of estimates The preparation of consolidated financial statements in conformity with United States generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from these estimates. Revenue recognition and allowance for doubtful accounts The Company's service offerings consist of on-net and off-net telecommunications services. Fixed fees are billed monthly in advance and usage fees are billed monthly in arrears. Revenues from telecommunication services are recognized when the services are performed, evidence of an arrangement exists, the fee is fixed and determinable and collection is probable. The probability of collection is determined by an analysis of credit history for certain new customers and historical payment patterns for existing customers. Service discounts and incentives related to telecommunication services are recorded as a reduction of revenue when granted. Fees billed in connection with customer installations are deferred and recognized ratably over the longer of the contract term or the estimated customer life. The Company expenses the direct costs associated with sales as incurred. The Company invoices certain customers for amounts contractually due for unfulfilled minimum contractual obligations and recognizes a corresponding sales allowance equal to the amount invoiced resulting in the recognition of no net revenue at the time the customer is billed. The Company vigorously seeks payment of these amounts. The Company recognizes revenue for these amounts as they are collected. The Company establishes an allowance for doubtful accounts and other sales credit adjustments related to its trade receivables. Trade receivables are recorded at the invoiced amount and can bear interest. Allowances for sales credits are established through a reduction of revenue, while allowances for doubtful accounts are established through a charge to selling, general, and administrative expenses as bad debt expense. The Company assesses the adequacy of these reserves by evaluating factors, such as the length of time individual receivables are past due, historical collection experience, and changes in the credit worthiness of its customers. The Company also assesses the ability of specific customers to meet their financial obligations and establishes specific allowances related to these customers. If circumstances relating to specific customers change or economic conditions change such that the Company's past collection experience and assessment of the economic environment are no longer appropriate, the Company's estimate of the recoverability of its trade receivables could be impacted. Accounts receivable balances are written-off against the allowance for doubtful accounts after all means of internal collection activities have been exhausted and the potential for recovery is considered remote. The Company recognized bad debt expense, net of recoveries, of $3.7 million, $2.8 million and $3.3 million for the years ended December 31, 2017, 2016 and 2015, respectively. Gross receipts taxes, universal service fund and other surcharges Revenue recognition standards include guidance relating to taxes or surcharges assessed by a governmental authority that are directly imposed on a revenue-producing transaction between a seller and a customer and may include, but are not limited to, gross receipts taxes, excise taxes, Universal Service Fund fees and certain state regulatory fees. Such charges may be presented gross or net based upon the Company's accounting policy election. The Company records certain excise taxes and surcharges on a gross basis and includes them in its revenues and costs of network operations. Excise taxes and surcharges billed to customers and recorded on a gross basis (as service revenue and network operations expense) were $10.9 million, $9.1 million, and $3.6 million for the years ended December 31, 2017, 2016 and 2015, respectively. Network operations Network operations expenses include the costs of personnel and related operating expenses associated with service delivery, network management, and customer support, network facilities costs, fiber and equipment maintenance fees, leased circuit costs, access fees paid to building owners and certain excise taxes and surcharges recorded on a gross basis. The Company estimates its accruals for any disputed leased circuit obligations based upon the nature and age of the dispute. Network operations costs are impacted by the timing and amounts of disputed circuit costs. The Company generally records these disputed amounts when billed by the vendor and reverses these amounts when the vendor credit has been received or the dispute has otherwise been resolved. The Company does not allocate depreciation and amortization expense to its network operations expense. Foreign currency translation adjustment and comprehensive income (loss) The consolidated financial statements of the Company's non-US operations are translated into US dollars using the period-end foreign currency exchange rates for assets and liabilities and the average foreign currency exchange rates for revenues and expenses. Gains and losses on translation of the accounts are accumulated and reported as a component of other comprehensive income (loss) in stockholders' equity. The Company's only components of "other comprehensive income (loss)" are currency translation adjustments for all periods presented. The Company considers the majority of its investments in its foreign subsidiaries to be long-term in nature. The Company's foreign exchange transaction gains (losses) are included within interest income and other on the consolidated statements of comprehensive income (loss). Financial instruments The Company considers all highly liquid investments with an original maturity of three months or less at purchase to be cash equivalents. The Company determines the appropriate classification of its investments at the time of purchase and evaluates such designation at each balance sheet date. At December 31, 2017 and December 31, 2016, the carrying amount of cash and cash equivalents, accounts receivable, prepaid and other current assets, accounts payable, and accrued expenses approximated fair value because of the short-term nature of these instruments. The Company measures its cash equivalents at amortized cost, which approximates fair value based upon quoted market prices (Level 1). Based upon recent trading prices (Level 2—market approach) at December 31, 2017 the fair value of the Company's $189.2 million senior unsecured notes was $193.0 million and the fair value of the Company's $375.0 million senior secured notes was $392.8 million. The Company was party to letters of credit totaling $0.7 million as of December 31, 2017 and $0.1 million as of December 31, 2016. These letters of credit are secured by investments that are restricted and included in deposits and other assets. Concentrations of credit risk The Company's assets that are exposed to credit risk consist of its cash and cash equivalents, other assets and accounts receivable. As of December 31, 2017 and 2016, the Company's cash equivalents were invested in demand deposit accounts, overnight investments and money market funds. The Company places its cash equivalents in instruments that meet high-quality credit standards as specified in the Company's investment policy guidelines. Accounts receivable are due from customers located in major metropolitan areas in the United States, Europe, Canada, Mexico and Asia. Receivables from the Company's net-centric (wholesale) customers are generally subject to a higher degree of credit risk than the Company's corporate customers. The Company relies upon an equipment vendor for the majority of its network equipment and is also dependent upon many third-party fiber providers for providing its services to its customers. Property and equipment Property and equipment are recorded at cost and depreciated once deployed using the straight-line method over the estimated useful lives of the assets. Useful lives are determined based on historical usage with consideration given to technological changes and trends in the industry that could impact the asset utilization. System infrastructure costs include the capitalized compensation costs of employees directly involved with construction activities and costs incurred by third party contractors. Assets and liabilities under capital leases are recorded at the lesser of the present value of the aggregate future minimum lease payments or the fair value of the assets under lease. Leasehold improvements include costs associated with building improvements. The Company determines the number of renewal option periods, if any, included in the lease term for purposes of amortizing leasehold improvements and the lease term of its capital leases based upon its assessment at the inception of the lease for which the failure to renew the lease imposes a penalty on the Company in such amount that a renewal appears to be reasonably assured. Expenditures for maintenance and repairs are expensed as incurred. Depreciation and amortization periods are as follows: Type of asset Depreciation or amortization period Indefeasible rights of use (IRUs) Shorter of useful life or the IRU lease agreement; generally 15 to 20 years Network equipment 3 to 8 years Leasehold improvements Shorter of lease term, including reasonably assured renewal periods, or useful life Software 5 years Owned buildings 40 years Office and other equipment 3 to 7 years System infrastructure 5 to 10 years Long-lived assets The Company's long-lived assets include property and equipment. These long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. Impairment is determined by comparing the carrying value of these long-lived assets to management's probability weighted estimate of the future undiscounted cash flows expected to result from the use of the assets. In the event an impairment exists, a loss is recognized based on the amount by which the carrying value exceeds the fair value of the asset, which would be determined by using quoted market prices or valuation techniques such as the discounted present value of expected future cash flows, appraisals, or other pricing models. In the event there are changes in the planned use of the Company's long-term assets or the Company's expected future undiscounted cash flows are reduced significantly, the Company's assessment of its ability to recover the carrying value of these assets could change. Equity-based compensation The Company recognizes compensation expense for its share-based payments granted to its employees based on their grant date fair values with the expense being recognized on a straight-line basis over the requisite service period. The Company begins recording equity-based compensation expense related to performance awards when it is considered probable that the performance conditions will be met and for market based awards compensation cost is recognized if the service condition is satisfied even if the market condition is not satisfied. Equity-based compensation expense is recognized in the statement of operations in a manner consistent with the classification of the employee's salary and other compensation. Income taxes The Company's deferred tax assets or liabilities are computed based upon the differences between financial statement and income tax bases of assets and liabilities using the enacted marginal tax rate. Deferred income tax expenses or benefits are based upon the changes in the assets or liability from period to period. At each balance sheet date, the Company assesses the likelihood that it will be able to realize its deferred tax assets. Valuation allowances are established when management determines that it is "more likely than not" that some portion or all of the deferred tax asset may not be realized. The Company considers all available positive and negative evidence in assessing the need for a valuation allowance including its historical operating results, ongoing tax planning, and forecasts of future taxable income, on a jurisdiction by jurisdiction basis. The Company reduces its valuation allowance if the Company concludes that it is "more likely than not" that it would be able to realize its deferred tax assets. Management determines whether a tax position is more likely than not to be sustained upon examination based on the technical merits of the position. Once it is determined that a position meets this recognition threshold, the position is measured to determine the amount of benefit to be recognized in the financial statements. The Company adjusts its estimated liabilities for uncertain tax positions periodically because of ongoing examinations by, and settlements with, the various taxing authorities, as well as changes in tax laws, regulations and interpretations. The Company's policy is to recognize interest and penalties accrued on any unrecognized tax benefits as a component of its income tax expense. Basic and diluted net income per common share Basic earnings per share ("EPS") excludes dilution for common stock equivalents and is computed by dividing net income or (loss) available to common stockholders by the weighted-average number of common shares outstanding for the period. Diluted EPS is based on the weighted-average number of shares of common stock outstanding during each period, adjusted for the effect of dilutive common stock equivalents. Shares of restricted stock are included in the computation of basic EPS as they vest and are included in diluted EPS, to the extent they are dilutive, determined using the treasury stock method. The following details the determination of the diluted weighted average shares: Year Ended Year Ended Year Ended Weighted average common shares—basic Dilutive effect of stock options Dilutive effect of restricted stock ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares—diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following details unvested shares of restricted common stock as well as the anti-dilutive effects of stock options and restricted stock awards outstanding: December 31, December 31, December 31, Unvested shares of restricted common stock Anti-dilutive options for common stock Anti-dilutive shares of restricted common stock Recent Accounting Pronouncements—to be Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases ("ASU 2016-02"). ASU 2016-02 will replace most existing lease accounting guidance when it becomes effective. ASU 2016-02 is effective for the Company beginning on January 1, 2019. Early application is permitted. ASU 2016-02 currently must be adopted using the modified retrospective approach for all leases that exist at or commence after the beginning of the earliest comparative period presented (with the option to apply certain practical expedients), which for the Company will be the period beginning January 1, 2017. However, in January 2018 the FASB issued a Proposed Accounting Standards Update which, among other changes, and if approved would allow a company to elect to adopt ASU 2016-02 using a cumulative effect adjustment to the opening balance of its retained earnings on the adoption date. ASU 2016-02 will require the Company to record a right to use asset and a lease liability for most of its leases, including its leases currently treated as operating leases. The Company is evaluating the effect that ASU 2016-02 will have on its consolidated financial statements and related disclosures and the Company will elect to apply certain practical expedients. The Company has not yet determined the effect of ASU 2016-02 on its ongoing financial reporting or quantified the impact to its balance sheet, however it does expect the right to use asset and lease liability recorded will be material. The Company does not expect to early adopt ASU 2016-02 and anticipates adopting ASU 2016-02 using the cumulative effect method should this method be approved. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , ("ASU 2014-09") which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers, and also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenues and cash flows from contracts with customers. ASU 2014-09 will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. ASU 2014-09 is effective for the Company on January 1, 2018. Early application is permitted for annual periods beginning after December 15, 2016. ASU 2014-09 permits the use of either the full retrospective or modified retrospective transition method. The Company will adopt ASU 2014-09 using the modified retrospective transition method on January 1, 2018 for those contracts that are not completed as of the date of the initial application. Under the modified retrospective method, the cumulative effect of applying the standard will be recognized at the date of initial application. The Company will not early adopt ASU 2014-09. The Company has not fully quantified the effect of adopting ASU 2014-09, however anticipates that the period for which it recognizes revenue for fees billed in connection with its customer installations will change and the Company will be required to capitalize certain contract acquisition costs. Revenues will be recognized over the contract term for installation fees associated with customer contracts with terms that are longer than month-to-month, which may be a shorter period than the average customer life currently used, because the fee does not give rise to a material right as defined by ASU 2014-09. Revenues will be recognized over the estimated average customer life for installation fees associated with month-to-month contracts, because the fee represents a material right. The impact of adopting ASU 2014-09 on the Company's total service revenue is not expected to be material. Additionally, the Company will be required to capitalize certain contract acquisition costs, including commissions paid to its sales team and agents, and to amortize these costs over the period the services are transferred to the customer for commission paid to its sales team and over the remaining contract term for agent commissions. The Company currently expenses these contract acquisition costs as incurred in Selling, General and Administrative Expenses. In June 2016, the FASB issued ASU 2016-13, " Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments". This guidance is intended to introduce a revised approach to the recognition and measurement of credit losses, emphasizing an updated model based on expected losses rather than incurred losses. This new standard is effective for annual and interim reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its financial statements and related disclosures.

Property and equipment_

Property and equipment:	12 Months Ended
	Dec. 31, 2017
Property and equipment:
Property and equipment:	2. Property and equipment: Property and equipment consisted of the following (in thousands): December 31, 2017 2016 Owned assets: Network equipment $ $ Leasehold improvements System infrastructure Software Office and other equipment Building Land ​ ​ ​ ​ ​ ​ ​ ​ Less—Accumulated depreciation and amortization ) ) ​ ​ ​ ​ ​ ​ ​ ​ Assets under capital leases: IRUs Less—Accumulated depreciation and amortization ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property and equipment, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation and amortization expense related to property and equipment and capital leases was $75.9 million, $75.2 million and $70.5 million, for 2017, 2016 and 2015, respectively. The Company capitalizes the compensation cost of employees directly involved with its construction activities. In 2017, 2016 and 2015, the Company capitalized compensation costs of $9.7 million, $8.7 million and $8.3 million respectively. These amounts are included in system infrastructure costs. Exchange agreement In 2017, 2016 and 2015 the Company exchanged certain used network equipment and cash consideration for new network equipment. The fair value of the new network equipment received was estimated to be $9.1 million, $15.5 million and $17.9 million resulting in gains of $3.9 million, $7.7 million and $5.3 million respectively. The estimated fair value of the equipment received was based upon the cash consideration price the Company pays for the new network equipment on a standalone basis (Level 3). Installment payment agreement In March 2015, the Company entered into an installment payment agreement ("IPA") with a vendor. Under the IPA the Company may purchase network equipment in exchange for interest free note obligations each with a twenty-four month term. There are no payments under each note obligation for the first six months followed by eighteen equal installment payments for the remaining eighteen month term. As of December 31, 2017 and December 31, 2016, there was $10.7 million and $5.5 million, respectively, of note obligations outstanding under the IPA, secured by the related equipment. The Company recorded the assets purchased and the present value of the note obligation utilizing an imputed interest rate. The resulting discounts totaling $0.4 million and $0.3 million as of December 31, 2017 and December 31, 2016, respectively, under the note obligations are being amortized over the note term using the effective interest rate method.

Accrued and other liabilities_

Accrued and other liabilities:	12 Months Ended
	Dec. 31, 2017
Accrued and other liabilities:
Accrued and other liabilities:	3. Accrued and other liabilities: Accrued and other current liabilities consist of the following (in thousands): December 31, 2017 2016 Operating accruals $ $ Deferred revenue—current portion Payroll and benefits Taxes—non-income based Interest ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Long-term debt_

Long-term debt:	12 Months Ended
	Dec. 31, 2017
Long-term debt:
Long-term debt:	4. Long-term debt: Debt extinguishment, redemption and new debt issuances—$375 million 2022 Notes In March 2015, Group redeemed its $240.0 million 8.375% senior notes due in 2018 (the "2018 Notes") with the proceeds from its February 2015 issuance of $250.0 million of 5.375% senior secured notes (the "2022 Notes") and existing cash on hand. The net proceeds from the offering were $248.6 million after deducting discounts and commissions and offering expenses. In February 2015 the Company deposited $251.6 million with the trustee for the benefit of the holders of the 2018 Notes in order to redeem on March 12, 2015 the entire outstanding amount of 2018 Notes at a redemption price of 104.188% of the $240.0 million principal amount thereof plus accrued interest. As a result of this transaction the Company incurred a loss on debt extinguishment and redemption of $10.1 million. In December 2016, the Company issued an additional $125.0 million par value of its 2022 Notes at a premium of 100.375% of par value. The Company received net proceeds of $124.3 million after deducting $1.2 million of offering costs. The $0.5 million premium is amortized as a reduction to interest expense to the maturity date using the effective interest rate method. The net proceeds from these offerings are intended to be used for general corporate purposes. The 2022 Notes were sold in private offerings for resale to qualified institutional buyers pursuant to SEC Rule 144A and mature on March 1, 2022. Interest accrues at 5.375% beginning on February 20, 2015 and is paid semi-annually in arrears on March 1 and September 1 of each year. The indenture governing the 2022 Notes provides that the Company and each of the Company's existing domestic subsidiaries and future material domestic subsidiaries guarantee the 2022 Notes, subject to certain exceptions and permitted liens. The 2022 Notes are also secured by a pledge of all of the equity interests in Group's domestic subsidiaries and 65% of the equity interests in Group's first-tier foreign subsidiaries. The 2022 Notes and the subsidiary guarantees will be the Company's and the subsidiary guarantors' senior indebtedness and will rank pari passu in right of payment with all of the Company's and the subsidiary guarantors' existing and future senior indebtedness, effectively senior to Group's senior unsecured indebtedness to the extent of the value of the collateral securing the 2022 Notes and the subsidiary guarantees, including Group's 2021 Notes that were issued on April 9, 2014, described below, and senior to any of the Company's and the subsidiary guarantors' future subordinated indebtedness. The 2022 Notes are structurally subordinated to the liabilities of the non-guarantor subsidiaries and are effectively subordinated to the Company's and the subsidiary guarantors' secured indebtedness to the extent of the value of the collateral securing such indebtedness on a basis senior to the 2022 Notes and the subsidiary guarantees. Holdings is also a guarantor of the 2022 Notes; however Holdings' guarantee is unsecured and thus its guarantee is not secured by any of Holdings assets. Holdings is also not subject to the covenants under the indenture governing the 2022 Notes. The 2022 Notes may be redeemed prior to December 1, 2021 (three months prior to the maturity date of the Notes) in whole or from time to time in part, at a redemption price equal to the sum of (1) 100% of the principal amount plus accrued and unpaid interest, if any, to, but not including, the redemption date, and (2) a make-whole premium, if any. The make-whole premium is the excess of (1) the net present value, on the redemption date, of the principal being redeemed or paid and the amount of interest (exclusive of interest accrued to the date of redemption) that would have been payable if such redemption had not been made, over (2) the aggregate principal amount of the notes being redeemed or paid. Net present value shall be determined by discounting, on a semi-annual basis, such principal and interest at the reinvestment rate (as determined in the indenture governing the 2022 Notes) from the respective dates on which such principal and interest would have been payable if such redemption had not been made. In addition, at any time on or after December 1, 2021 (three months prior to the maturity date of the 2022 Notes), the Issuer may redeem the 2022 Notes, in whole and or in part, at a redemption price equal to 100% of the principal amount of the 2022 Notes to be redeemed, plus accrued and unpaid interest, if any, to, but not including, the redemption date. Senior unsecured notes—$189.2 million 2021 Notes On April 9, 2014, Cogent Communications Finance, Inc. ("Cogent Finance"), a newly formed financing subsidiary of Group, completed an offering at par of $200.0 million in aggregate principal amount of 5.625% Senior Notes due 2021 (the "2021 Notes"). The 2021 Notes were sold in private offerings for resale to qualified institutional buyers pursuant to SEC Rule 144A. The offering closed into escrow pursuant to an escrow agreement, dated as of April 9, 2014 (the "Escrow Agreement"). The term "Issuer" refers to Cogent Finance prior to the release of the funds from the escrow account (such date of release, the "Escrow Release Date") and to Group after the Escrow Release Date. As a condition to releasing the funds from escrow Group redeemed its remaining outstanding convertible notes on June 20, 2014 (the "Redemption Transaction"). After consummation of the Redemption Transaction, Cogent Finance merged with Group, with Group continuing as the surviving corporation (the "Finance Merger"). At the time of consummation of the Finance Merger, Group assumed the obligations of Cogent Finance under the 2021 Notes and the indenture governing the 2021 Notes (the "Indenture") and Group and each of Group's domestic subsidiaries became party to the Indenture pursuant to a supplemental indenture to the Indenture and the obligations under the Indenture became obligations solely of Group and each of Group's domestic subsidiaries. Holdings also provided a guarantee of the 2021 Notes but Holdings is not subject to the covenants under the Indenture. After the conditions to the release of the escrow proceeds were satisfied, on June 25, 2014 (the "Escrow Release Date") the proceeds from the 2021 Notes were released. The net proceeds from the offering were $195.8 million after deducting commissions and offering expenses. The net proceeds from the offering are intended to be used for general corporate purposes. In the second quarter of 2016, the Company paid $10.9 million for the purchase of $10.8 million of par value and accrued interest on its 2021 Notes reducing the principal amount to $189.2 million and resulting in a loss of $0.2 million. The loss resulted from the write off of the remaining unamortized debt issuance costs related to the purchased notes. The 2021 Notes were issued pursuant to, and are governed by the Indenture between Cogent Finance and the trustee. The 2021 Notes bear interest at a rate of 5.625% per year and will mature on April 15, 2021. Interest began to accrue on the 2021 Notes on April 9, 2014 and will be paid semi-annually on April 15 and October 15, commencing on October 15, 2014. Following the Escrow Release Date, the 2021 Notes became Group's senior unsecured obligations and are guaranteed on a senior unsecured basis by Holdings. The 2021 Notes are effectively subordinated in right of payment to all of Group's and each guarantor's secured indebtedness and future secured indebtedness, if any, to the extent of the value of the assets securing such indebtedness. The 2021 Notes are equal in right of payment with Group's and each guarantor's unsecured indebtedness that is not subordinated in right of payment to the 2021 Notes. The 2021 Notes rank senior in right of payment to Group's and each guarantor's future subordinated debt, if any; and are structurally subordinated in right of payment to all indebtedness and other liabilities of any of the Group's subsidiaries that are not guarantors, which only consist of immaterial subsidiaries and foreign subsidiaries that do not guarantee other indebtedness of Group. Group may also redeem the 2021 Notes, in whole or in part, at any time on or after April 15, 2017 at the applicable redemption prices specified under the indenture governing the 2021 Notes plus accrued and unpaid interest, if any, to the date of redemption. The redemption prices (expressed as a percentage of the principal amount) are 104.219% during the 12-month period beginning on April 15, 2017, 102.813% during the 12-month period beginning on April 15, 2018, 101.406% during the 12-month period beginning on April 15, 2019 and 100.0% during the 12-month period beginning on April 15, 2020 and thereafter. If Group experiences specific kinds of changes of control, Group must offer to repurchase all of the 2021 Notes at a purchase price of 101.0% of their principal amount, plus accrued and unpaid interest, if any, to the repurchase date. Limitations under the indentures The indentures governing the 2022 Notes and 2021 Notes, among other things, limit the Company's ability to incur indebtedness; to pay dividends or make other distributions; to make certain investments and other restricted payments; to create liens; consolidate, merge, sell or otherwise dispose of all or substantially all of its assets; to incur restrictions on the ability of a subsidiary to pay dividends or make other payments; and to enter into certain transactions with its affiliates. Limitations on the ability to incur additional indebtedness (excluding IRU agreements incurred in the normal course of business) include a restriction on incurring additional indebtedness if the Company's consolidated leverage ratio, as defined in the indentures, is greater than 5.0. The indentures prohibit certain payments, such as dividends and stock purchases, when the Company's consolidated leverage ratio, as defined by the indentures, is greater than 4.25. A certain amount of such unrestricted payments is permitted notwithstanding this prohibition. The unrestricted payment amount may be increased by the Company's consolidated cash flow, as defined in the indentures, as long as the Company's consolidated leverage ratio is less than 4.25. The Company's consolidated leverage ratio is currently above 4.25 as of December 31, 2017. As of December 31, 2017, a total of $64.3 million is permitted for investment payments including dividends and stock purchases. Senior secured notes—2018 Notes The Company redeemed its 8.375% Senior Secured Notes (the "2018 Notes") in March 2015 at a redemption price of 104.188% of the $240.0 million principal amount thereof plus accrued interest. On January 26, 2011 and on August 19, 2013, the Company issued its 2018 Notes due February 15, 2018, for aggregate principal amounts of $175.0 million and $65.0 million, respectively, in private offerings for resale to qualified institutional buyers pursuant to SEC Rule 144A. The 2018 Notes were secured and bore interest at 8.375% per annum. Interest was payable in cash semiannually in arrears on February 15 and August 15, of each year. The 2018 Notes sold in August 2013 were sold at 109.00% of par value. The $5.9 million premium was being amortized as a reduction to interest expense to the maturity date using the effective interest rate method. Long-term debt maturities The aggregate future contractual maturities of long-term debt were as follows as of December 31, 2017 (in thousands): For the year ending December 31, 2018 $ 2019 2020 — 2021 2022 Thereafter — ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Income taxes_

Income taxes:	12 Months Ended
	Dec. 31, 2017
Income taxes:
Income taxes:	5. Income taxes: On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (the "Act"). The Act amends the Internal Revenue Code and reduces the corporate tax rate from a maximum of 35% to a flat 21% rate. The rate reduction is effective on January 1, 2018. The Company's net deferred tax assets represent a decrease in corporate taxes expected to be paid in the future. Under generally accepted accounting principles deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company's net deferred tax asset was determined based on the current enacted federal tax rate of 35% prior to the passage of the Act. As a result of the reduction in the corporate income tax rate from 35% to 21% and other provisions under the Act, the Company has made reasonable estimates of the effects of the Act and revalued its net deferred tax asset on a provisional basis at December 31, 2017 resulting in a reduction in the value of its net deferred tax asset of approximately $9.0 million and recorded at transition tax of $2.3 million related to its foreign operations for a total of $11.3 million, which was recorded as additional noncash income tax expense in the three months and year ended December 31, 2017. Although the tax rate reduction is known, the Company has not collected all of the necessary data to complete its analysis of the effect of the Tax Act on the underlying deferred taxes and as such, the amounts recorded as of December 31, 2017 are provisional. The actual impact on the Company's net deferred tax asset may vary from this amount from certain changes in interpretations of the Act, additional guidance issued by the U.S. Treasury Department, the IRS, and other standard-setting bodies, additional data collected and assumptions that the Company has made. Those adjustments may materially impact our provision for income taxes and effective tax rate in the period in which the adjustments are made. The accounting for the tax effects of the Tax Act will be completed in 2018. The components of income (loss) before income taxes consist of the following (in thousands): Years Ended December 31, 2017 2016 2015 Domestic $ $ $ Foreign ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income before income taxes $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The income tax expense is comprised of the following (in thousands): Years Ended December 31, 2017 2016 2015 Current: Federal $ — $ $ ) State ) ) Foreign ) ) ) Deferred: Federal ) ) ) State ) ) ) Foreign ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income tax expense $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Our consolidated temporary differences comprising our net deferred tax assets are as follows (in thousands): December 31, 2017 2016 Deferred Tax Assets: Net operating loss carry-forwards $ $ Tax credits Equity-based compensation ​ ​ ​ ​ ​ ​ ​ ​ Total gross deferred tax assets ​ ​ ​ ​ ​ ​ ​ ​ Deferred Tax Liabilities: Depreciation and amortization Accrued liabilities and other ​ ​ ​ ​ ​ ​ ​ ​ Total gross deferred tax liabilities ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets before valuation allowance Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ At each balance sheet date, the Company assesses the likelihood that it will be able to realize its deferred tax assets. The Company considers all available positive and negative evidence in assessing the need for a valuation allowance. The Company maintains a full valuation allowance against certain of its deferred tax assets consisting primarily of net operating loss carryforwards related to its foreign operations in Canada, Europe and Asia and net operating losses in the United States that are limited for use under Section 382 of the Internal Revenue Code. As of December 31, 2017, the Company has combined net operating loss carry-forwards of $1.0 billion. This amount includes federal net operating loss carry-forwards in the United States of $150.9 million, net operating loss carry-forwards related to its European, Mexican, Asian and Canadian operations of $868.6 million, $5.3 million, $2.1 million and $1.0 million, respectively. Section 382 of the Internal Revenue Code in the United States limits the utilization of net operating losses when ownership changes, as defined by that section, occur. The Company has performed an analysis of its Section 382 ownership changes and has determined that the utilization of certain of its net operating loss carryforwards in the United States is limited based on the annual Section 382 limitation and remaining carryforward period. Of the $150.9 million of net operating losses available at December 31, 2017 in the United States $60.1 million are limited for use under Section 382. Net operating loss carryforwards outside of the United States totaling $877.0 million are not subject to limitations similar to Section 382. The net operating loss carryforwards in the United States will expire, if unused, between 2025 and 2037. The net operating loss carry-forwards related to the Company's Mexican, Asian and Canadian operations will expire if unused, between 2019 and 2027. The net operating loss carry-forwards related to the Company's European operations include $722.9 million that do not expire and $145.7 million that expire between 2018 and 2032. Other than the $2.3 million transition tax recorded in the year ended December 31, 2017 as a result of its foreign earnings the Company has not provided for United States deferred income taxes or foreign withholding taxes on its undistributed earnings for certain non-US subsidiaries earnings or cumulative translation adjustments because these earnings and adjustments are intended to be permanently reinvested in operations outside the United States. It is not practical to determine the amount of the unrecognized deferred tax liability on such undistributed earnings or cumulative translation adjustments. In the normal course of business the Company takes positions on its tax returns that may be challenged by taxing authorities. The Company evaluates all uncertain tax positions to assess whether the position will more likely than not be sustained upon examination. If the Company determines that the tax position is not more likely than not to be sustained, the Company records a liability for the amount of the benefit that is not more likely than not to be realized when the tax position is settled. The Company does not expect that its liability for uncertain tax positions will increase during the twelve months ended December 31, 2018, however, actual changes in the liability for uncertain tax positions could be different than currently expected. If recognized, changes in the Company's total unrecognized tax benefits would impact the Company's effective income tax rate. The roll-forward of the liability for uncertain tax positions is below and excludes interest and penalties. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Years Ended 2017 2016 2015 Beginning balance of unrecognized tax benefits $ — $ $ Decrease attributable to settlements with taxing authorities — ) — Decrease attributable to lapses of statutes of limitation — — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Ending balance of unrecognized tax benefits $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The Company or one of its subsidiaries files income tax returns in the US federal jurisdiction and various state and foreign jurisdictions. The Company is subject to US federal tax and state tax examinations for years 2004 to 2017. The Company is subject to tax examinations in its foreign jurisdictions generally for years 2005 to 2017. The following is a reconciliation of the Federal statutory income taxes to the amounts reported in the financial statements (in thousands). Years Ended December 31, 2017 2016 2015 Federal income tax expense at statutory rates $ ) $ ) $ ) Effect of: State income taxes, net of federal benefit ) ) ) Impact of foreign operations ) Non-deductible expenses ) ) ) Changes in tax reserves — Federal tax rate change ) — — Transition tax on foreign earnings ) — — Other ) Changes in valuation allowance ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax expense $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Commitments and contingencies_

Commitments and contingencies:	12 Months Ended
	Dec. 31, 2017
Commitments and contingencies:
Commitments and contingencies:	6. Commitments and contingencies: Capital leases—fiber lease agreements The Company has entered into lease agreements with numerous providers of dark fiber primarily under 15-20 year IRUs typically with additional renewal terms. Once the Company has accepted the related fiber route, leases that meet the criteria for treatment as capital leases are recorded as a capital lease obligation and an IRU asset. The interest rate used in determining the present value of the aggregate future minimum lease payments is the lessee's incremental borrowing rate for the lease term. The future minimum payments (principal and interest) under these agreements are as follows (in thousands): For the year ending December 31, 2018 $ 2019 2020 2021 2022 Thereafter ​ ​ ​ ​ ​ Total minimum lease obligations Less—amounts representing interest ) ​ ​ ​ ​ ​ Present value of minimum lease obligations Current maturities ) ​ ​ ​ ​ ​ Capital lease obligations, net of current maturities $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gains on capital lease terminations In March 2015 the Company elected to terminate certain IRU capital lease obligations in Spain. The Company obtained alternative fiber to serve its customers in Spain. Under its estimate of the termination provisions of the related contracts the Company has recorded an estimated termination liability of $9.0 million included in accrued and other current liabilities. The difference between the remaining carrying amount of the related IRU capital lease liabilities ($29.9 million), the remaining net book value of the IRU assets ($10.0 million) and the termination liability and amounts due through the termination date was recorded as a gain on capital lease terminations of $10.1 million in 2015. In July 2015, the Company settled a dispute for the payment of the remaining balances for certain IRU capital lease obligations in Europe. The IRU assets were fully depreciated in 2012 when the related fiber was replaced and was no longer used by the Company. The difference between the remaining net present value of the related IRU capital lease obligations ($1.8 million) and the settlement liability ($0.4 million) was recorded as a $1.4 million gain on capital lease terminations in 2015. Current and potential litigation In accordance with the accounting guidance for contingencies, the Company accrues its estimate of a contingent liability when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Where it is probable that a liability has been incurred and there is a range of expected loss for which no amount in the range is more likely than any other amount, the Company accrues at the low end of the range. The Company reviews its accruals at least quarterly and adjusts them to reflect the impact of negotiations, settlements, rulings, advice of legal counsel, and other information and events pertaining to a particular matter. The Company has taken certain positions related to its obligations for leased circuits for which it is reasonably possible could result in a loss of up to $2.6 million in excess of the amount accrued at December 31, 2017. In December 2011, certain former sales employees of the Company filed a collective action against the Company in the United States District Court, Southern District of Texas, Houston Division alleging misclassification of the Company's sales employees throughout the United States in violation of the Fair Labor Standards Act. The lawsuit sought to recover pay for allegedly unpaid overtime and other damages, including attorney's fees. In March 2014, the judge de-certified the collective action. Each of the former employees that opted-in to the collective action retained the right to file an individual action. Approximately 70 former employees did so. The Company has settled a number of the cases that were filed and made the required settlement payments the final of which was settled for $3.1 million and paid in October 2017. The Company is engaged in an arbitration proceeding in Spain in which a former provider of optical fiber to the Company is seeking approximately $9 million for the Company's early termination of the optical fiber leases, which amount the Company has accrued in 2015. The Company has counterclaimed for damages and is contesting its obligation to pay the termination liability in an arbitration proceeding in Spain. The arbitration is being conducted by the Civil and Commercial Arbitration Court (CIMA) in Madrid, Spain. In the ordinary course of business the Company is involved in other legal activities and claims. Because such matters are subject to many uncertainties and the outcomes are not predictable with assurance, the liability related to these legal actions and claims cannot be determined with certainty. Management does not believe that such claims and actions will have a material impact on the Company's financial condition or results of operations. Judgment is required in estimating the ultimate outcome of any dispute resolution process, as well as any other amounts that may be incurred to conclude the negotiations or settle any litigation. Actual results may differ from these estimates under different assumptions or conditions and such differences could be material. Operating leases The Company leases office space, network equipment sites, and data center facilities under operating leases. In certain cases the Company enters into operating lease commitments for fiber. Future minimum annual payments under these arrangements are as follows (in thousands): For the year ending December 31, 2018 $ 2019 2020 2021 2022 Thereafter ​ ​ ​ ​ ​ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Expenses related to these arrangements were $38.2 million in 2017, $34.6 million in 2016 and $38.2 million in 2015. Unconditional purchase obligations Unconditional purchase obligations for equipment and services totaled $5.0 million at December 31, 2017. As of December 31, 2017, the Company had also committed to additional dark fiber IRU capital and operating lease agreements totaling $14.8 million in future payments to be paid over periods of up to 20 years. These obligations begin when the related fiber is accepted, which is generally expected to occur in 2018. Future minimum payments under these obligations are $8.4 million, $0.3 million, $0.4 million, $0.4 million and $0.4 million for the years ending December 31, 2018 to December 31, 2022, respectively, and $9.9 million, thereafter. Defined contribution plan The Company sponsors a 401(k) defined contribution plan that provides for a Company matching payment. The Company matching payments were $0.7 million for 2017, $0.6 million for 2016 and $0.6 million for 2015 and were paid in cash.

Stockholders' equity_

Stockholders' equity:	12 Months Ended
	Dec. 31, 2017
Stockholders' equity:
Stockholders' equity:	7. Stockholders' equity: Authorized shares The Company has 75.0 million shares of authorized $0.001 par value common stock and 10,000 authorized but unissued shares of $0.001 par value preferred stock. The holders of common stock are entitled to one vote per common share and, subject to any rights of any series of preferred stock, dividends may be declared and paid on the common stock when determined by the Company's Board of Directors. Common stock buybacks The Company's Board of Directors has approved $50.0 million for purchases of the Company's common stock under a buyback program (the "Buyback Program"). At December 31, 2017, there was $41.5 million remaining for purchases under the Buyback Program. During 2017, 2016 and 2015, the Company purchased approximately 0.1 million, 0.1 million and 1.2 million shares of its common stock for $1.8 million, $4.5 million and $39.4 million, respectively. These common shares were subsequently retired. Dividends on common stock Dividends are recorded as a reduction to retained earnings. Dividends on unvested restricted shares of common stock are paid as the awards vest. The Company's initial quarterly dividend payment was made in the third quarter of 2012. The payment of any future dividends and any other returns of capital, including stock buybacks, will be at the discretion of the Company's Board of Directors and may be reduced, eliminated or increased and will be dependent upon the Company's financial position, results of operations, available cash, cash flow, capital requirements, limitations under the Company's debt indentures and other factors deemed relevant by the Company's Board of Directors. The Company is a Delaware Corporation and under the General Corporate Law of the State of Delaware distributions may be restricted including a restriction that distributions, including stock purchases and dividends, do not result in an impairment of a corporation's capital, as defined under Delaware Law. The indentures governing the Company's notes limit the Company's ability to return cash to its stockholders.

Stock option and award plan_

Stock option and award plan:	12 Months Ended
	Dec. 31, 2017
Stock option and award plan:
Stock option and award plan:	8. Stock option and award plan: Incentive award plan The Company grants restricted stock and options for common stock under its award plan, as amended (the "Award Plan"). In May 2017, the Company's shareholders approved a 1.2 million share increase to the authorized shares under the Award Plan. Stock options granted under the Award Plan generally vest over a four-year period and have a term of ten years. Grants of shares of restricted stock granted under the Award Plan generally vest over periods ranging from three to four years. Compensation expense for all awards is recognized over the service period. Awards with graded vesting terms that are subject only to service conditions are recognized on a straight-line basis. Certain option and share grants provide for accelerated vesting if there is a change in control, as defined. For grants of restricted stock, when an employee terminates prior to full vesting the employee retains their vested shares and the employees' unvested shares are returned to the plan. For grants of options for common stock, when an employee terminates prior to full vesting, the employee may elect to exercise their vested options for a period of ninety days and any unvested options are returned to the plan. Shares issued to satisfy awards are provided from the Company's authorized shares. In May 2016 the Company granted 73,450 restricted shares under the Award Plan with a grant date fair value of $2.9 million that are subject to certain performance conditions and cliff vesting based upon certain of the Company's operating metrics and will be recognized as equity-based compensation expense on a straight line basis over the service period. In the second quarter of 2017 the Company granted a total of 470,404 shares under the Award Plan to certain of its employees and directors with a grant date fair value of $19.0 million. The grant date fair value will be recognized as equity-based compensation expense on a straight line basis over the respective service periods. The vesting of certain of these shares (24,050) granted to the Company's executives is subject to performance conditions and the vesting of 105,000 shares granted to the Company's CEO are subject to the total shareholder return of the Company's common stock compared to the total shareholder return of the Nasdaq Telecommunications Index. The accounting for equity-based compensation expense requires the Company to make estimates and judgments that affect its financial statements. These estimates include the following. Expected Dividend Yield—The Company uses an expected dividend yield based upon expected annual dividends and the Company's stock price. Expected Volatility—The Company uses its historical volatility for a period commensurate with the expected term of the option. Risk-Free Interest Rate—The Company uses the zero coupon US Treasury rate during the quarter having a term that most closely resembles the expected term of the option. Expected Term of the Option—The Company estimates the expected life of the option term by analyzing historical stock option exercises. Forfeiture Rates—The Company estimates its forfeiture rate based on historical data with further consideration given to the class of employees to whom the options or shares were granted. The weighted-average per share grant date fair value of options was $7.06 in 2017, $6.23 in 2016 and $6.29 in 2015. The following assumptions were used for determining the fair value of options granted in the three years ended December 31, 2017: Years Ended Black-Scholes Assumptions 2017 2016 2015 Dividend yield % % % Expected volatility % % % Risk-free interest rate % % % Expected life of the option term (in years) Stock option activity under the Company's Award Plan during the year ended December 31, 2017, was as follows: Number of Weighted-Average Outstanding at December 31, 2016 $ Granted $ Cancelled and expired ) $ Exercised—intrinsic value $0.5 million; cash received $1.2 million ) $ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2017—$1.8 million intrinsic value and 7.5 years weighted-average remaining contractual term $ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2017—$1.4 million intrinsic value and 6.4 years weighted-average remaining contractual term $ ​ ​ ​ ​ ​ ​ ​ ​ Expected to vest—$1.7 million intrinsic value and 7.3 years weighted-average remaining contractual term $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ A summary of the Company's non-vested restricted stock awards as of December 31, 2017 and the changes during the year ended December 31, 2017 are as follows: Non-vested awards Shares Weighted-Average Non-vested at December 31, 2016 $ Granted $ Vested ) $ Forfeited ) $ ​ ​ ​ ​ ​ ​ ​ ​ Non-vested at December 31, 2017 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The weighted average per share grant date fair value of restricted stock granted was $40.52 in 2017 (0.5 million shares) $38.87 in 2016 (0.4 million shares) and $33.19 in 2015 (0.1 million shares). The fair value was determined using the quoted market price of the Company's common stock on the date of grant. The fair value of shares of restricted stock vested in 2017, 2016 and 2015 was $12.6 million $12.0 million and $14.3 million, respectively. Equity-based compensation expense related to stock options and restricted stock was $13.3 million, $10.7 million, and $11.5 million for 2017, 2016, and 2015, respectively. The income tax benefit related to stock options and restricted stock was $2.5 million, $2.8 million, and $1.8 million for 2017, 2016, and 2015, respectively. The Company capitalized compensation expense related to stock options and restricted stock for 2017, 2016, and 2015 of $1.2 million, $1.2 million and $1.0 million, respectively. As of December 31, 2017, there was $26.4 million of total unrecognized compensation cost related to non-vested equity-based compensation awards. That cost is expected to be recognized over a weighted average period of 2.1 years.

Related party transactions_

Related party transactions:	12 Months Ended
	Dec. 31, 2017
Related party transactions:
Related party transactions:	9. Related party transactions: Office lease The Company's headquarters was located in an office building owned by Niobium LLC (a successor to 6715 Kenilworth Avenue Partnership). The two owners of Niobium LLC are the Company's Chief Executive Officer, David Schaeffer, who has a 51% interest in Niobium LLC and his wife who has a 49% interest. The lease was scheduled to end on August 31, 2016 and was cancellable by the Company upon 60 days' notice. The Company terminated the lease effective as of May 10, 2015. In April 2015, the Company entered into a new lease agreement for its headquarters building with Sodium LLC whose two owners are the Company's Chief Executive Officer, who has a 51% interest in Sodium LLC and his wife who has a 49% interest. The Company moved into the new headquarters building in May 2015. The fixed annual rent for the new headquarters building is $1.0 million per year plus an allocation of taxes and utilities. The lease term is for five years and is cancellable by the Company upon 60 days' notice. The Company's audit committee reviews and approves all transactions with related parties. The Company paid $1.6 million in 2017, $1.7 million in 2016 and $1.2 million in 2015, respectively for rent and related costs (including taxes and utilities) to these lessors for these leases, respectively.

Geographic information_

Geographic information:	12 Months Ended
	Dec. 31, 2017
Geographic information:
Geographic information:	10. Geographic information: Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and in assessing the Company's performance. The Company has one operating segment. Revenues are attributed to regions based on where the services are provided. Below are the Company's service revenues and long lived assets by geographic region (in thousands): Years Ended December 31, 2017 2016 2015 Service Revenue North America $ $ $ Europe ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, December 31, Long lived assets, net North America $ $ $ Europe $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The majority of North American revenue consists of services delivered within the United States.

Quarterly financial information

Quarterly financial information (unaudited):	12 Months Ended
	Dec. 31, 2017
Quarterly financial information (unaudited):
Quarterly financial information (unaudited):	11. Quarterly financial information (unaudited): Three months ended March 31, June 30, September 30, December 31, (in thousands, except share and per share amounts) Service revenue $ $ $ $ Network operations, including equity-based compensation expense Gains on equipment transactions Operating income Net income (loss) ) Net income (loss) per common share—basic and diluted ) Weighted-average number of common shares—basic Weighted-average number of common shares—diluted (a) See Note 5 for the impact of the increase in income tax expense during the three months ended December 31, 2017. Three months ended March 31, June 30, September 30, December 31, (in thousands, except share and per share amounts) Service revenue $ $ $ $ Network operations, including equity-based compensation expense Gains on equipment transactions Operating income Net income Net income per common share—basic and diluted Weighted-average number of common shares—basic Weighted-average number of common shares—diluted

Subsequent Events_

Subsequent Events:	12 Months Ended
	Dec. 31, 2017
Subsequent Events:
Subsequent Events:	12. Subsequent Events: Dividend On February 21, 2018, the Company's Board of Directors approved the payment of its quarterly dividend of $0.50 per common share. The dividend for the first quarter of 2018 will be paid to holders of record on March 9, 2018. This estimated $22.4 million dividend payment is expected to be made on March 26, 2018. Share Grant In February 2018 the Company granted approximately 0.3 million shares under the Award Plan to certain of its employees and directors with a grant date fair value of approximately $14.1 million. The grant date fair value will be recognized as equity-based compensation expense on a straight line basis over the respective service periods. The vesting of certain of these shares (24,050) granted to the Company's executives is subject to performance conditions and the vesting of 105,000 shares granted to the Company's CEO are subject to the total shareholder return of the Company's common stock compared to the total shareholder return of the Nasdaq Telecommunications Index.

Schedule II VALUATION AND QUALI

Schedule II VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Dec. 31, 2017
Schedule II VALUATION AND QUALIFYING ACCOUNTS
Schedule II VALUATION AND QUALIFYING ACCOUNTS	Schedule II Description Balance at Charged to (Deductions) Balance at Allowance for doubtful service accounts receivable (deducted from accounts receivable)(a) Year ended December 31, 2015 $ $ $ ) $ Year ended December 31, 2016 $ $ $ ) $ Year ended December 31, 2017 $ $ $ ) $ Deferred tax valuation allowance Year ended December 31, 2015 $ $ $ ) $ Year ended December 31, 2016 $ $ $ ) $ Year ended December 31, 2017 $ $ $ ) $ (a) Bad debt expense, net of recoveries, was approximately $3.7 million for the year ended December 31, 2017, $2.8 million for the year ended December 31, 2016 and $3.3 million for the year ended December 31, 2015.

Description of the business a22

Description of the business and summary of significant accounting policies: (Policies)	12 Months Ended
	Dec. 31, 2017
Description of the business and summary of significant accounting policies:
Principles of consolidation	Principles of consolidation The consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles and include the accounts of the Company and all of its wholly-owned and majority-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Use of estimates	Use of estimates The preparation of consolidated financial statements in conformity with United States generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from these estimates.
Revenue recognition	Revenue recognition and allowance for doubtful accounts The Company's service offerings consist of on-net and off-net telecommunications services. Fixed fees are billed monthly in advance and usage fees are billed monthly in arrears. Revenues from telecommunication services are recognized when the services are performed, evidence of an arrangement exists, the fee is fixed and determinable and collection is probable. The probability of collection is determined by an analysis of credit history for certain new customers and historical payment patterns for existing customers. Service discounts and incentives related to telecommunication services are recorded as a reduction of revenue when granted. Fees billed in connection with customer installations are deferred and recognized ratably over the longer of the contract term or the estimated customer life. The Company expenses the direct costs associated with sales as incurred. The Company invoices certain customers for amounts contractually due for unfulfilled minimum contractual obligations and recognizes a corresponding sales allowance equal to the amount invoiced resulting in the recognition of no net revenue at the time the customer is billed. The Company vigorously seeks payment of these amounts. The Company recognizes revenue for these amounts as they are collected. The Company establishes an allowance for doubtful accounts and other sales credit adjustments related to its trade receivables. Trade receivables are recorded at the invoiced amount and can bear interest. Allowances for sales credits are established through a reduction of revenue, while allowances for doubtful accounts are established through a charge to selling, general, and administrative expenses as bad debt expense. The Company assesses the adequacy of these reserves by evaluating factors, such as the length of time individual receivables are past due, historical collection experience, and changes in the credit worthiness of its customers. The Company also assesses the ability of specific customers to meet their financial obligations and establishes specific allowances related to these customers. If circumstances relating to specific customers change or economic conditions change such that the Company's past collection experience and assessment of the economic environment are no longer appropriate, the Company's estimate of the recoverability of its trade receivables could be impacted. Accounts receivable balances are written-off against the allowance for doubtful accounts after all means of internal collection activities have been exhausted and the potential for recovery is considered remote. The Company recognized bad debt expense, net of recoveries, of $3.7 million, $2.8 million and $3.3 million for the years ended December 31, 2017, 2016 and 2015, respectively.
Allowance for doubtful accounts	Revenue recognition and allowance for doubtful accounts The Company's service offerings consist of on-net and off-net telecommunications services. Fixed fees are billed monthly in advance and usage fees are billed monthly in arrears. Revenues from telecommunication services are recognized when the services are performed, evidence of an arrangement exists, the fee is fixed and determinable and collection is probable. The probability of collection is determined by an analysis of credit history for certain new customers and historical payment patterns for existing customers. Service discounts and incentives related to telecommunication services are recorded as a reduction of revenue when granted. Fees billed in connection with customer installations are deferred and recognized ratably over the longer of the contract term or the estimated customer life. The Company expenses the direct costs associated with sales as incurred. The Company invoices certain customers for amounts contractually due for unfulfilled minimum contractual obligations and recognizes a corresponding sales allowance equal to the amount invoiced resulting in the recognition of no net revenue at the time the customer is billed. The Company vigorously seeks payment of these amounts. The Company recognizes revenue for these amounts as they are collected. The Company establishes an allowance for doubtful accounts and other sales credit adjustments related to its trade receivables. Trade receivables are recorded at the invoiced amount and can bear interest. Allowances for sales credits are established through a reduction of revenue, while allowances for doubtful accounts are established through a charge to selling, general, and administrative expenses as bad debt expense. The Company assesses the adequacy of these reserves by evaluating factors, such as the length of time individual receivables are past due, historical collection experience, and changes in the credit worthiness of its customers. The Company also assesses the ability of specific customers to meet their financial obligations and establishes specific allowances related to these customers. If circumstances relating to specific customers change or economic conditions change such that the Company's past collection experience and assessment of the economic environment are no longer appropriate, the Company's estimate of the recoverability of its trade receivables could be impacted. Accounts receivable balances are written-off against the allowance for doubtful accounts after all means of internal collection activities have been exhausted and the potential for recovery is considered remote. The Company recognized bad debt expense, net of recoveries, of $3.7 million, $2.8 million and $3.3 million for the years ended December 31, 2017, 2016 and 2015, respectively.
Gross receipts taxes, universal service fund and other surcharges	Gross receipts taxes, universal service fund and other surcharges Revenue recognition standards include guidance relating to taxes or surcharges assessed by a governmental authority that are directly imposed on a revenue-producing transaction between a seller and a customer and may include, but are not limited to, gross receipts taxes, excise taxes, Universal Service Fund fees and certain state regulatory fees. Such charges may be presented gross or net based upon the Company's accounting policy election. The Company records certain excise taxes and surcharges on a gross basis and includes them in its revenues and costs of network operations. Excise taxes and surcharges billed to customers and recorded on a gross basis (as service revenue and network operations expense) were $10.9 million, $9.1 million, and $3.6 million for the years ended December 31, 2017, 2016 and 2015, respectively.
Network operations	Network operations Network operations expenses include the costs of personnel and related operating expenses associated with service delivery, network management, and customer support, network facilities costs, fiber and equipment maintenance fees, leased circuit costs, access fees paid to building owners and certain excise taxes and surcharges recorded on a gross basis. The Company estimates its accruals for any disputed leased circuit obligations based upon the nature and age of the dispute. Network operations costs are impacted by the timing and amounts of disputed circuit costs. The Company generally records these disputed amounts when billed by the vendor and reverses these amounts when the vendor credit has been received or the dispute has otherwise been resolved. The Company does not allocate depreciation and amortization expense to its network operations expense.
Foreign currency translation adjustment and comprehensive income (loss)	Foreign currency translation adjustment and comprehensive income (loss) The consolidated financial statements of the Company's non-US operations are translated into US dollars using the period-end foreign currency exchange rates for assets and liabilities and the average foreign currency exchange rates for revenues and expenses. Gains and losses on translation of the accounts are accumulated and reported as a component of other comprehensive income (loss) in stockholders' equity. The Company's only components of "other comprehensive income (loss)" are currency translation adjustments for all periods presented. The Company considers the majority of its investments in its foreign subsidiaries to be long-term in nature. The Company's foreign exchange transaction gains (losses) are included within interest income and other on the consolidated statements of comprehensive income (loss).
Financial instruments	Financial instruments The Company considers all highly liquid investments with an original maturity of three months or less at purchase to be cash equivalents. The Company determines the appropriate classification of its investments at the time of purchase and evaluates such designation at each balance sheet date. At December 31, 2017 and December 31, 2016, the carrying amount of cash and cash equivalents, accounts receivable, prepaid and other current assets, accounts payable, and accrued expenses approximated fair value because of the short-term nature of these instruments. The Company measures its cash equivalents at amortized cost, which approximates fair value based upon quoted market prices (Level 1). Based upon recent trading prices (Level 2—market approach) at December 31, 2017 the fair value of the Company's $189.2 million senior unsecured notes was $193.0 million and the fair value of the Company's $375.0 million senior secured notes was $392.8 million. The Company was party to letters of credit totaling $0.7 million as of December 31, 2017 and $0.1 million as of December 31, 2016. These letters of credit are secured by investments that are restricted and included in deposits and other assets.
Concentrations of credit risk	Concentrations of credit risk The Company's assets that are exposed to credit risk consist of its cash and cash equivalents, other assets and accounts receivable. As of December 31, 2017 and 2016, the Company's cash equivalents were invested in demand deposit accounts, overnight investments and money market funds. The Company places its cash equivalents in instruments that meet high-quality credit standards as specified in the Company's investment policy guidelines. Accounts receivable are due from customers located in major metropolitan areas in the United States, Europe, Canada, Mexico and Asia. Receivables from the Company's net-centric (wholesale) customers are generally subject to a higher degree of credit risk than the Company's corporate customers. The Company relies upon an equipment vendor for the majority of its network equipment and is also dependent upon many third-party fiber providers for providing its services to its customers.
Property and equipment	Property and equipment Property and equipment are recorded at cost and depreciated once deployed using the straight-line method over the estimated useful lives of the assets. Useful lives are determined based on historical usage with consideration given to technological changes and trends in the industry that could impact the asset utilization. System infrastructure costs include the capitalized compensation costs of employees directly involved with construction activities and costs incurred by third party contractors. Assets and liabilities under capital leases are recorded at the lesser of the present value of the aggregate future minimum lease payments or the fair value of the assets under lease. Leasehold improvements include costs associated with building improvements. The Company determines the number of renewal option periods, if any, included in the lease term for purposes of amortizing leasehold improvements and the lease term of its capital leases based upon its assessment at the inception of the lease for which the failure to renew the lease imposes a penalty on the Company in such amount that a renewal appears to be reasonably assured. Expenditures for maintenance and repairs are expensed as incurred. Depreciation and amortization periods are as follows: Type of asset Depreciation or amortization period Indefeasible rights of use (IRUs) Shorter of useful life or the IRU lease agreement; generally 15 to 20 years Network equipment 3 to 8 years Leasehold improvements Shorter of lease term, including reasonably assured renewal periods, or useful life Software 5 years Owned buildings 40 years Office and other equipment 3 to 7 years System infrastructure 5 to 10 years
Long-lived assets	Long-lived assets The Company's long-lived assets include property and equipment. These long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. Impairment is determined by comparing the carrying value of these long-lived assets to management's probability weighted estimate of the future undiscounted cash flows expected to result from the use of the assets. In the event an impairment exists, a loss is recognized based on the amount by which the carrying value exceeds the fair value of the asset, which would be determined by using quoted market prices or valuation techniques such as the discounted present value of expected future cash flows, appraisals, or other pricing models. In the event there are changes in the planned use of the Company's long-term assets or the Company's expected future undiscounted cash flows are reduced significantly, the Company's assessment of its ability to recover the carrying value of these assets could change.
Equity-based compensation	Equity-based compensation The Company recognizes compensation expense for its share-based payments granted to its employees based on their grant date fair values with the expense being recognized on a straight-line basis over the requisite service period. The Company begins recording equity-based compensation expense related to performance awards when it is considered probable that the performance conditions will be met and for market based awards compensation cost is recognized if the service condition is satisfied even if the market condition is not satisfied. Equity-based compensation expense is recognized in the statement of operations in a manner consistent with the classification of the employee's salary and other compensation.
Income taxes	Income taxes The Company's deferred tax assets or liabilities are computed based upon the differences between financial statement and income tax bases of assets and liabilities using the enacted marginal tax rate. Deferred income tax expenses or benefits are based upon the changes in the assets or liability from period to period. At each balance sheet date, the Company assesses the likelihood that it will be able to realize its deferred tax assets. Valuation allowances are established when management determines that it is "more likely than not" that some portion or all of the deferred tax asset may not be realized. The Company considers all available positive and negative evidence in assessing the need for a valuation allowance including its historical operating results, ongoing tax planning, and forecasts of future taxable income, on a jurisdiction by jurisdiction basis. The Company reduces its valuation allowance if the Company concludes that it is "more likely than not" that it would be able to realize its deferred tax assets. Management determines whether a tax position is more likely than not to be sustained upon examination based on the technical merits of the position. Once it is determined that a position meets this recognition threshold, the position is measured to determine the amount of benefit to be recognized in the financial statements. The Company adjusts its estimated liabilities for uncertain tax positions periodically because of ongoing examinations by, and settlements with, the various taxing authorities, as well as changes in tax laws, regulations and interpretations. The Company's policy is to recognize interest and penalties accrued on any unrecognized tax benefits as a component of its income tax expense.
Basic and diluted net income per common share	Basic and diluted net income per common share Basic earnings per share ("EPS") excludes dilution for common stock equivalents and is computed by dividing net income or (loss) available to common stockholders by the weighted-average number of common shares outstanding for the period. Diluted EPS is based on the weighted-average number of shares of common stock outstanding during each period, adjusted for the effect of dilutive common stock equivalents. Shares of restricted stock are included in the computation of basic EPS as they vest and are included in diluted EPS, to the extent they are dilutive, determined using the treasury stock method. The following details the determination of the diluted weighted average shares: Year Ended Year Ended Year Ended Weighted average common shares—basic Dilutive effect of stock options Dilutive effect of restricted stock ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares—diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following details unvested shares of restricted common stock as well as the anti-dilutive effects of stock options and restricted stock awards outstanding: December 31, December 31, December 31, Unvested shares of restricted common stock Anti-dilutive options for common stock Anti-dilutive shares of restricted common stock
Recent Accounting Pronouncements - to be Adopted	Recent Accounting Pronouncements—to be Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases ("ASU 2016-02"). ASU 2016-02 will replace most existing lease accounting guidance when it becomes effective. ASU 2016-02 is effective for the Company beginning on January 1, 2019. Early application is permitted. ASU 2016-02 currently must be adopted using the modified retrospective approach for all leases that exist at or commence after the beginning of the earliest comparative period presented (with the option to apply certain practical expedients), which for the Company will be the period beginning January 1, 2017. However, in January 2018 the FASB issued a Proposed Accounting Standards Update which, among other changes, and if approved would allow a company to elect to adopt ASU 2016-02 using a cumulative effect adjustment to the opening balance of its retained earnings on the adoption date. ASU 2016-02 will require the Company to record a right to use asset and a lease liability for most of its leases, including its leases currently treated as operating leases. The Company is evaluating the effect that ASU 2016-02 will have on its consolidated financial statements and related disclosures and the Company will elect to apply certain practical expedients. The Company has not yet determined the effect of ASU 2016-02 on its ongoing financial reporting or quantified the impact to its balance sheet, however it does expect the right to use asset and lease liability recorded will be material. The Company does not expect to early adopt ASU 2016-02 and anticipates adopting ASU 2016-02 using the cumulative effect method should this method be approved. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers , ("ASU 2014-09") which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers, and also requires enhanced disclosures regarding the nature, amount, timing and uncertainty of revenues and cash flows from contracts with customers. ASU 2014-09 will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. ASU 2014-09 is effective for the Company on January 1, 2018. Early application is permitted for annual periods beginning after December 15, 2016. ASU 2014-09 permits the use of either the full retrospective or modified retrospective transition method. The Company will adopt ASU 2014-09 using the modified retrospective transition method on January 1, 2018 for those contracts that are not completed as of the date of the initial application. Under the modified retrospective method, the cumulative effect of applying the standard will be recognized at the date of initial application. The Company will not early adopt ASU 2014-09. The Company has not fully quantified the effect of adopting ASU 2014-09, however anticipates that the period for which it recognizes revenue for fees billed in connection with its customer installations will change and the Company will be required to capitalize certain contract acquisition costs. Revenues will be recognized over the contract term for installation fees associated with customer contracts with terms that are longer than month-to-month, which may be a shorter period than the average customer life currently used, because the fee does not give rise to a material right as defined by ASU 2014-09. Revenues will be recognized over the estimated average customer life for installation fees associated with month-to-month contracts, because the fee represents a material right. The impact of adopting ASU 2014-09 on the Company's total service revenue is not expected to be material. Additionally, the Company will be required to capitalize certain contract acquisition costs, including commissions paid to its sales team and agents, and to amortize these costs over the period the services are transferred to the customer for commission paid to its sales team and over the remaining contract term for agent commissions. The Company currently expenses these contract acquisition costs as incurred in Selling, General and Administrative Expenses. In June 2016, the FASB issued ASU 2016-13, " Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments". This guidance is intended to introduce a revised approach to the recognition and measurement of credit losses, emphasizing an updated model based on expected losses rather than incurred losses. This new standard is effective for annual and interim reporting periods beginning after December 15, 2019 and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its financial statements and related disclosures.

Description of the business a23

Description of the business and summary of significant accounting policies: (Tables)	12 Months Ended
	Dec. 31, 2017
Description of the business and summary of significant accounting policies:
Schedule of depreciation and amortization periods	Type of asset Depreciation or amortization period Indefeasible rights of use (IRUs) Shorter of useful life or the IRU lease agreement; generally 15 to 20 years Network equipment 3 to 8 years Leasehold improvements Shorter of lease term, including reasonably assured renewal periods, or useful life Software 5 years Owned buildings 40 years Office and other equipment 3 to 7 years System infrastructure 5 to 10 years
Schedule of diluted weighted average shares	Year Ended Year Ended Year Ended Weighted average common shares—basic Dilutive effect of stock options Dilutive effect of restricted stock ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares—diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of unvested and anti-dilutive shares	December 31, December 31, December 31, Unvested shares of restricted common stock Anti-dilutive options for common stock Anti-dilutive shares of restricted common stock

Property and equipment_ (Tables

Property and equipment: (Tables)	12 Months Ended
	Dec. 31, 2017
Property and equipment:
Schedule of property and equipment	Property and equipment consisted of the following (in thousands): December 31, 2017 2016 Owned assets: Network equipment $ $ Leasehold improvements System infrastructure Software Office and other equipment Building Land ​ ​ ​ ​ ​ ​ ​ ​ Less—Accumulated depreciation and amortization ) ) ​ ​ ​ ​ ​ ​ ​ ​ Assets under capital leases: IRUs Less—Accumulated depreciation and amortization ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property and equipment, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Accrued and other liabilities_

Accrued and other liabilities: (Tables)	12 Months Ended
	Dec. 31, 2017
Accrued and other liabilities:
Schedule of accrued and other current liabilities	Accrued and other current liabilities consist of the following (in thousands): December 31, 2017 2016 Operating accruals $ $ Deferred revenue—current portion Payroll and benefits Taxes—non-income based Interest ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Long-term debt_ (Tables)

Long-term debt: (Tables)	12 Months Ended
	Dec. 31, 2017
Long-term debt:
Schedule of aggregate future contractual maturities of long-term debt	The aggregate future contractual maturities of long-term debt were as follows as of December 31, 2017 (in thousands): For the year ending December 31, 2018 $ 2019 2020 — 2021 2022 Thereafter — ​ ​ ​ ​ ​ Total $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Income taxes_ (Tables)

Income taxes: (Tables)	12 Months Ended
	Dec. 31, 2017
Income taxes:
Schedule of components of income (loss) before income taxes	The components of income (loss) before income taxes consist of the following (in thousands): Years Ended December 31, 2017 2016 2015 Domestic $ $ $ Foreign ) ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income before income taxes $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of income tax expense	The income tax expense is comprised of the following (in thousands): Years Ended December 31, 2017 2016 2015 Current: Federal $ — $ $ ) State ) ) Foreign ) ) ) Deferred: Federal ) ) ) State ) ) ) Foreign ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total income tax expense $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of net deferred tax assets	Our consolidated temporary differences comprising our net deferred tax assets are as follows (in thousands): December 31, 2017 2016 Deferred Tax Assets: Net operating loss carry-forwards $ $ Tax credits Equity-based compensation ​ ​ ​ ​ ​ ​ ​ ​ Total gross deferred tax assets ​ ​ ​ ​ ​ ​ ​ ​ Deferred Tax Liabilities: Depreciation and amortization Accrued liabilities and other ​ ​ ​ ​ ​ ​ ​ ​ Total gross deferred tax liabilities ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets before valuation allowance Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of reconciliation of unrecognized tax benefits	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): Years Ended 2017 2016 2015 Beginning balance of unrecognized tax benefits $ — $ $ Decrease attributable to settlements with taxing authorities — ) — Decrease attributable to lapses of statutes of limitation — — ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Ending balance of unrecognized tax benefits $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of reconciliation of the Federal statutory income taxes to the amounts reported in the financial statements	The following is a reconciliation of the Federal statutory income taxes to the amounts reported in the financial statements (in thousands). Years Ended December 31, 2017 2016 2015 Federal income tax expense at statutory rates $ ) $ ) $ ) Effect of: State income taxes, net of federal benefit ) ) ) Impact of foreign operations ) Non-deductible expenses ) ) ) Changes in tax reserves — Federal tax rate change ) — — Transition tax on foreign earnings ) — — Other ) Changes in valuation allowance ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax expense $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Commitments and contingencies_

Commitments and contingencies: (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and contingencies:
Schedule of future minimum annual payments under capital leases-fiber lease agreements	The future minimum payments (principal and interest) under these agreements are as follows (in thousands): For the year ending December 31, 2018 $ 2019 2020 2021 2022 Thereafter ​ ​ ​ ​ ​ Total minimum lease obligations Less—amounts representing interest ) ​ ​ ​ ​ ​ Present value of minimum lease obligations Current maturities ) ​ ​ ​ ​ ​ Capital lease obligations, net of current maturities $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of future minimum annual payments under operating leases and building access agreements	Future minimum annual payments under these arrangements are as follows (in thousands): For the year ending December 31, 2018 $ 2019 2020 2021 2022 Thereafter ​ ​ ​ ​ ​ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Stock option and award plan_ (T

Stock option and award plan: (Tables)	12 Months Ended
	Dec. 31, 2017
Stock option and award plan:
Schedule of assumptions used for determining the fair value of options granted	Years Ended Black-Scholes Assumptions 2017 2016 2015 Dividend yield % % % Expected volatility % % % Risk-free interest rate % % % Expected life of the option term (in years)
Schedule of stock option activity	Number of Weighted-Average Outstanding at December 31, 2016 $ Granted $ Cancelled and expired ) $ Exercised—intrinsic value $0.5 million; cash received $1.2 million ) $ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding at December 31, 2017—$1.8 million intrinsic value and 7.5 years weighted-average remaining contractual term $ ​ ​ ​ ​ ​ ​ ​ ​ Exercisable at December 31, 2017—$1.4 million intrinsic value and 6.4 years weighted-average remaining contractual term $ ​ ​ ​ ​ ​ ​ ​ ​ Expected to vest—$1.7 million intrinsic value and 7.3 years weighted-average remaining contractual term $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of non-vested restricted stock awards	Non-vested awards Shares Weighted-Average Non-vested at December 31, 2016 $ Granted $ Vested ) $ Forfeited ) $ ​ ​ ​ ​ ​ ​ ​ ​ Non-vested at December 31, 2017 $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Geographic information_ (Tables

Geographic information: (Tables)	12 Months Ended
	Dec. 31, 2017
Geographic information:
Schedule of service revenues and long lived assets by geographic region	Below are the Company's service revenues and long lived assets by geographic region (in thousands): Years Ended December 31, 2017 2016 2015 Service Revenue North America $ $ $ Europe ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, December 31, Long lived assets, net North America $ $ $ Europe $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Quarterly financial informati31

Quarterly financial information (unaudited): (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly financial information (unaudited):
Schedule of quarterly financial information	Three months ended March 31, June 30, September 30, December 31, (in thousands, except share and per share amounts) Service revenue $ $ $ $ Network operations, including equity-based compensation expense Gains on equipment transactions Operating income Net income (loss) ) Net income (loss) per common share—basic and diluted ) Weighted-average number of common shares—basic Weighted-average number of common shares—diluted (a) See Note 5 for the impact of the increase in income tax expense during the three months ended December 31, 2017. Three months ended March 31, June 30, September 30, December 31, (in thousands, except share and per share amounts) Service revenue $ $ $ $ Network operations, including equity-based compensation expense Gains on equipment transactions Operating income Net income Net income per common share—basic and diluted Weighted-average number of common shares—basic Weighted-average number of common shares—diluted

Description of the business a32

Description of the business and summary of significant accounting policies: Description of the business (Details)	12 Months Ended
	Dec. 31, 2017MB
Minimum
Speed per second of bandwidth (in megabits and gigabits)	100
Maximum
Speed per second of bandwidth (in megabits and gigabits)	100

Description of the business a33

Description of the business and summary of significant accounting policies: Revenue recognition - Allowance for doubtful accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Description of the business and summary of significant accounting policies:
Bad debt expense, net of recoveries	$ 3.7	$ 2.8	$ 3.3

Description of the business a34

Description of the business and summary of significant accounting policies: Revenue recognition - Excise taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Description of the business and summary of significant accounting policies:
Excise taxes and surcharge	$ 10.9	$ 9.1	$ 3.6

Description of the business a35

Description of the business and summary of significant accounting policies: Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Financial instruments
Letters of credit	$ 0.7	$ 0.1
Senior unsecured 2021 notes
Financial instruments
Senior notes	189.2
Senior unsecured 2021 notes | Level 2
Financial instruments
Senior notes, fair value	193
Senior secured 2022 notes
Financial instruments
Senior notes	375
Senior secured 2022 notes | Level 2
Financial instruments
Senior notes, fair value	$ 392.8

Description of the business a36

Description of the business and summary of significant accounting policies: Property and equipment (Details)	12 Months Ended
	Dec. 31, 2017
Indefeasible rights of use (IRUs) | Minimum
Property and equipment
Depreciation or amortization period	15 years
Indefeasible rights of use (IRUs) | Maximum
Property and equipment
Depreciation or amortization period	20 years
Network equipment | Minimum
Property and equipment
Depreciation or amortization period	3 years
Network equipment | Maximum
Property and equipment
Depreciation or amortization period	8 years
Software
Property and equipment
Depreciation or amortization period	5 years
Building
Property and equipment
Depreciation or amortization period	40 years
Office and other equipment | Minimum
Property and equipment
Depreciation or amortization period	3 years
Office and other equipment | Maximum
Property and equipment
Depreciation or amortization period	7 years
System infrastructure | Minimum
Property and equipment
Depreciation or amortization period	5 years
System infrastructure | Maximum
Property and equipment
Depreciation or amortization period	10 years

Description of the business a37

Description of the business and summary of significant accounting policies: Basic and diluted net income per common share (Details) - shares	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Diluted weighted average shares
Weighted-average common shares - basic (in shares)	44,844,469	44,767,163	44,717,372	44,649,645	44,577,826	44,574,583	44,491,899	44,402,640	44,855,263	44,641,805	44,888,723
Weighted average common shares-diluted	44,844,469	45,118,607	44,988,655	44,917,014	44,803,782	44,816,860	44,757,494	44,571,937	45,184,203	44,873,030	45,159,489
Stock options
Diluted weighted average shares
Dilutive effect (options or restricted stock)									31,534	31,760	40,196
Anti-dilutive effects
Anti-dilutive (options or restricted stock)									47,513	90,959	119,872
Restricted stock
Diluted weighted average shares
Dilutive effect (options or restricted stock)									297,406	199,465	230,570
Anti-dilutive effects
Unvested shares of restricted common stock	1,112,151				908,761				1,112,151	908,761	870,751
Anti-dilutive (options or restricted stock)									201	79,450	362,241

Property and equipment_ (Detail

Property and equipment: (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and equipment
Property and equipment, gross	$ 1,233,756	$ 1,136,470
Less -Accumulated depreciation and amortization	(852,474)	(774,829)
Total property and equipment, net	381,282	361,641
Depreciation and amortization	75,926	75,235	$ 70,527
Owned Assets
Property and equipment
Property and equipment, gross	850,296	786,550
Less -Accumulated depreciation and amortization	(680,114)	(621,162)
Total property and equipment, net	170,182	165,388
Network equipment | Owned Assets
Property and equipment
Property and equipment, gross	510,327	476,786
Leasehold improvements | Owned Assets
Property and equipment
Property and equipment, gross	200,184	182,734
System infrastructure | Owned Assets
Property and equipment
Property and equipment, gross	114,046	102,502
Compensation costs	9,700	8,700	$ 8,300
Software | Owned Assets
Property and equipment
Property and equipment, gross	9,701	9,523
Office and other equipment | Owned Assets
Property and equipment
Property and equipment, gross	14,591	13,735
Building | Owned Assets
Property and equipment
Property and equipment, gross	1,334	1,171
Land | Owned Assets
Property and equipment
Property and equipment, gross	113	99
Indefeasible rights of use (IRUs)
Property and equipment
Property and equipment, gross	383,460	349,920
Less -Accumulated depreciation and amortization	(172,360)	(153,667)
Total property and equipment, net	$ 211,100	$ 196,253

Property and equipment_ Exchang

Property and equipment: Exchange agreement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and equipment
Non-cash component of network equipment obtained in exchange transactions	$ 3,861	$ 7,739	$ 8,156
Network equipment
Property and equipment
Non-cash component of network equipment obtained in exchange transactions	3,900	7,700	5,300
Network equipment | Estimate | Level 3
Property and equipment
Fair value of equipment	$ 9,100	$ 15,500	$ 17,900

Property and equipment_ Install

Property and equipment: Installment payment agreement (Details) - Network equipment - Note obligations $ in Millions	1 Months Ended
	Mar. 31, 2016paymentinstallment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Installment payment agreement
Term of debt (in months)	24 months
Number of payments first six months | payment	0
Number of equal payments | installment	18
Outstanding obligation		$ 10.7	$ 5.5
Unamortized discount		$ 0.4	$ 0.3

Accrued and other liabilities41

Accrued and other liabilities: (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued and other liabilities:
Operating accruals	$ 25,278	$ 24,356
Deferred revenue -current portion	4,758	4,334
Payroll and benefits	5,139	4,170
Taxes-non-income based	2,360	4,037
Interest	10,412	10,252
Accrued Liabilities, Current, Total	$ 47,947	$ 47,149

Long-term debt_ Debt extinguish

Long-term debt: Debt extinguishment, redemption and new debt issuances - $375 million 2022 Notes- (Details) - USD ($) $ in Thousands	Mar. 12, 2015	Apr. 09, 2014	Dec. 31, 2016	Feb. 28, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2016	Mar. 31, 2015	Aug. 19, 2013	Jan. 26, 2011
Debt extinguishment, redemption and new debt issuances
Losses on debt extinguishment and redemption						$ (587)	$ (10,144)
Debt premium					$ 1,239	1,105	171
2018 Notes
Debt extinguishment, redemption and new debt issuances
Redemption face amount	$ 240,000
Face amount									$ 240,000	$ 65,000	$ 175,000
Interest rate (as a percent)									8.375%	8.375%	8.375%
Repurchased amount including interest				$ 251,600
Principal amount plus accrued and unpaid interest (as a percent)	104.188%
Losses on debt extinguishment and redemption	$ (10,100)
Senior secured 2022 notes
Debt extinguishment, redemption and new debt issuances
Face amount			$ 125,000	$ 250,000		125,000
Interest rate (as a percent)				5.375%
Net proceeds			$ 124,300	$ 248,600
Premium of par value, in percent			100.375%
Offering costs						$ 1,202	$ 1,397
Debt premium			$ 500
Equity interest in foreign entities as collateral (in percent)					65.00%
Senior unsecured 2021 notes
Debt extinguishment, redemption and new debt issuances
Face amount		$ 200,000						$ 189,200
Interest rate (as a percent)		5.625%
Net proceeds		$ 195,800
Prior to December 1, 2021 | Senior secured 2022 notes
Debt extinguishment, redemption and new debt issuances
Principal amount plus accrued and unpaid interest (as a percent)					100.00%
On or after December 1, 2021 | Senior secured 2022 notes
Debt extinguishment, redemption and new debt issuances
Principal amount plus accrued and unpaid interest (as a percent)					100.00%

Long-term debt_ Senior unsecure

Long-term debt: Senior unsecured notes - $189.2 million 2021 Notes (Details) - Senior unsecured 2021 notes - USD ($) $ in Millions	Apr. 09, 2014	Jun. 30, 2016	Dec. 31, 2017
Senior unsecured notes- $189.2 million 2021 Notes
Principal amount	$ 200	$ 189.2
Interest rate (as a percent)	5.625%
Net proceeds	$ 195.8
Interest expense on original debt		10.9
Interest expense on repurchased debt		10.8
Loss on debt purchases		$ (0.2)
Percentage of principal amount at which notes will be required to be repurchased in the event of a change of control			101.00%
12-month period beginning on April 15, 2017
Senior unsecured notes- $189.2 million 2021 Notes
Principal amount plus accrued and unpaid interest (as a percent)			104.219%
12-month period beginning on April 15, 2018
Senior unsecured notes- $189.2 million 2021 Notes
Principal amount plus accrued and unpaid interest (as a percent)			102.813%
12-month period beginning on April 15, 2019
Senior unsecured notes- $189.2 million 2021 Notes
Principal amount plus accrued and unpaid interest (as a percent)			101.406%
12-month period beginning on April 15, 2020
Senior unsecured notes- $189.2 million 2021 Notes
Principal amount plus accrued and unpaid interest (as a percent)			100.00%

Long-term debt_ Limitations und

Long-term debt: Limitations under the Indentures (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Limitations under the Indentures
Consolidated leverage ratio	4.25
Permitted investments and payments	$ 64.3
Restriction on incurring additional indebtedness | Minimum
Limitations under the Indentures
Consolidated leverage ratio	5
Restriction on certain payments | Minimum
Limitations under the Indentures
Consolidated leverage ratio	4.25
Increase in unrestricted payment amount | Maximum
Limitations under the Indentures
Consolidated leverage ratio	4.25

Long-term debt_ Senior secured

Long-term debt: Senior secured notes - 2018 Notes (Details) - 2018 Notes - USD ($) $ in Millions	Mar. 12, 2015	Aug. 19, 2013	Mar. 31, 2015	Jan. 26, 2011
Senior secured notes-2018 Notes
Interest rate (as a percent)		8.375%	8.375%	8.375%
Principal amount plus accrued and unpaid interest (as a percent)	104.188%
Face amount		$ 65	$ 240	$ 175
Par value premium (in percent)		109.00%
Debt premium		$ 5.9

Long-term debt_ Long-term debt

Long-term debt: Long-term debt maturities (Details) $ in Thousands	Dec. 31, 2017USD ($)
Long-term debt:
2,018	$ 8,153
2,019	2,595
2,021	189,225
2,022	375,000
Total	$ 574,973

Income taxes_ Tax Cuts and Jobs

Income taxes: Tax Cuts and Jobs Act (Details) - USD ($) $ in Thousands	Jan. 01, 2018	Dec. 31, 2017
Income taxes:
Federal income tax at statutory rates (as a percent)	21.00%	35.00%
Reduction in the value of net deferred tax asset		$ 9,000
Transition tax		2,296
Noncash income tax expense		$ 11,300

Income taxes_ Components of inc

Income taxes: Components of income (loss) before income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Components of income (loss) before income taxes
Domestic	$ 52,250	$ 41,759	$ 21,972
Foreign	(21,132)	(17,499)	(9,260)
Income before income taxes	$ 31,118	$ 24,260	$ 12,712

Income taxes_ Income tax expens

Income taxes: Income tax expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal		$ 135	$ (9)
State	$ (353)	(188)	4
Foreign	(209)	(202)	(96)
Deferred:
Federal	(24,150)	(8,175)	(5,867)
State	(430)	(1,047)	(1,959)
Foreign	(100)	146	111
Total income tax expense	$ (25,242)	$ (9,331)	$ (7,816)

Income taxes_ Temporary differe

Income taxes: Temporary differences (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets:
Net operating loss carry-forwards	$ 271,219	$ 273,509
Tax credits	2,771	2,237
Equity-based compensation	2,327	2,279
Total gross deferred tax assets	276,317	278,025
Deferred Tax Liabilities:
Depreciation and amortization	22,777	29,984
Accrued liabilities and other	106,251	95,606
Total gross deferred tax liabilities	129,028	125,590
Deferred tax assets (liabilities)
Net deferred tax assets before valuation allowance	147,289	152,435
Valuation allowance	(129,673)	(110,194)
Net deferred tax assets	$ 17,616	$ 42,241

Income taxes_ Loss carry-forwar

Income taxes: Loss carry-forwards (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Net operating loss carry-forwards
Net operating loss carry-forwards	$ 1,000,000
Transition tax	2,296
United States
Net operating loss carry-forwards
Net operating loss carry-forwards	150,900
Net operating loss carry-forwards not available for use	60,100
Europe
Net operating loss carry-forwards
Net operating loss carry-forwards	868,600
Net operating loss carry-forwards not subject to expiration	722,900
Net operating loss carry-forwards subject to expiration	145,700
Mexico
Net operating loss carry-forwards
Net operating loss carry-forwards	5,300
Asian
Net operating loss carry-forwards
Net operating loss carry-forwards	2,100
Canada
Net operating loss carry-forwards
Net operating loss carry-forwards	1,000
Other than United States
Net operating loss carry-forwards
Net operating loss carry-forwards	$ 877,000

Income taxes_ Reconciliation of

Income taxes: Reconciliation of unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the beginning and ending amount of unrecognized tax benefits (excluding interest and penalties)
Beginning balance of unrecognized tax benefits	$ 776	$ 866
Decrease attributable to settlements with taxing authorities	$ (776)
Decrease attributable to lapses of statutes of limitation		(90)
Ending balance of unrecognized tax benefits		$ 776

Income taxes_ Effective Income

Income taxes: Effective Income Tax Rate Reconciliation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)subsidiary	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Income taxes:
Number of potential subsidiaries filing income tax returns | subsidiary	1
Reconciliation of the Federal statutory income taxes to the amounts reported in the financial statements
Federal income tax expense at statutory rates	$ (10,892)	$ (8,492)	$ (4,450)
State income tax, net of federal benefit	(2,244)	(1,080)	(1,710)
Impact of foreign operations	74	138	(179)
Non-deductible expenses	(1,350)	(590)	(1,253)
Changes in tax reserves		175	128
Federal tax rate change	(9,046)
Transition tax on foreign earnings	(2,296)
Other	239	98	(16)
Change in valuation allowance	273	420	(336)
Total income tax expense	$ (25,242)	$ (9,331)	$ (7,816)

Commitments and contingencies54

Commitments and contingencies: Capital leases - fiber lease agreement (Details) - Indefeasible rights of use (IRUs)	12 Months Ended
	Dec. 31, 2017
Minimum
Commitments and contingencies
Capital lease term	15 years
Maximum
Commitments and contingencies
Capital lease term	20 years

Commitments and contingencies55

Commitments and contingencies: Capital leases - future minimum payments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Future minimum payments under capital lease agreements
2,018	$ 23,969
2,019	22,953
2,020	22,954
2,021	22,491
2,022	21,228
Thereafter	222,080
Total minimum lease obligations	335,675
Less-amounts representing interest	(178,171)
Present value of minimum lease obligations	157,504
Current maturities	(7,171)	$ (6,626)
Capital lease obligations, net of current maturities	$ 150,333	$ 135,335

Commitments and contingencies56

Commitments and contingencies: Gains on capital lease terminations (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Jul. 31, 2015	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Gains on capital lease terminations
Net book value				$ 381,282	$ 361,641
Gains on capital lease terminations			$ 11,643
Europe
Gains on capital lease terminations
Carrying value	$ 1,800
Settlement liability	(400)
Gains on capital lease terminations	$ 1,400
Spain
Gains on capital lease terminations
Estimate of possible loss		$ 9,000
Carrying value		29,900
Net book value		10,000
Gains on capital lease terminations		$ 10,100

Commitments and contingencies57

Commitments and contingencies: Current and potential litigation (Details) $ in Millions	1 Months Ended
	Oct. 31, 2017USD ($)	Dec. 31, 2011USD ($)employee	Dec. 31, 2017USD ($)	Mar. 31, 2015USD ($)
Commitments and contingencies
Estimate of possible loss in excess of accrual			$ 2.6
Number of former employees | employee		70
Settlement amount		$ 3.1
Settlement payment	$ 3.1
Spain
Commitments and contingencies
Estimate of possible loss				$ 9

Commitments and contingencies58

Commitments and contingencies: Operating leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and contingencies:
2,018	$ 37,276
2,019	27,347
2,020	22,170
2,021	17,717
2,022	11,875
Thereafter	35,538
Total minimum lease obligations	151,923
Expenses related to arrangements
Expenses related to operating lease arrangements	$ 38,200	$ 34,600	$ 38,200

Commitments and contingencies59

Commitments and contingencies: Unconditional purchase obligations (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Unconditional purchase obligations
Maximum period of maintenance payment	20 years
2,018	$ 8.4
2,019	0.3
2,020	0.4
2,021	0.4
2,022	0.4
Thereafter	9.9
Unconditional purchase obligation	14.8
Equipment and services
Unconditional purchase obligations
Unconditional purchase obligation	$ 5

Commitments and contingencies60

Commitments and contingencies: Defined contribution plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and contingencies:
Matching cash payments towards defined contribution plan	$ 0.7	$ 0.6	$ 0.6

Stockholders' equity_ Authorize

Stockholders' equity: Authorized shares (Details)	12 Months Ended
	Dec. 31, 2017Vote / shares$ / sharesshares	Dec. 31, 2016$ / sharesshares
Stockholders' equity:
Common stock, shares authorized | shares	75,000,000	75,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001
Preferred stock, authorized but unissued shares (in shares) | shares	10,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.001
Voting rights per common share | Vote / shares	1

Stockholders' equity_ Common st

Stockholders' equity: Common stock buybacks (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stockholders' equity:
Authorized amount for common stock repurchases	$ 50
Remaining authorized amount for common stock repurchases	$ 41.5
Repurchase of common stock (in shares)	0.1	0.1	1.2
Cost of repurchase of common stock	$ 1.8	$ 4.5	$ 39.4

Stock option and award plan_ In

Stock option and award plan: Incentive award plan (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
	Feb. 28, 2018	May 31, 2017	May 31, 2016	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Incentive award plan
Share increase (in shares)		1,200,000
Stock options
Incentive award plan
Vesting period					4 years
Expiration period					10 years
Exercise period of options vested, when an employee is terminated prior to full vesting					90 days
Granted (in shares)				470,404
Fair value of shares				$ 19
Restricted stock
Incentive award plan
Granted (in shares)			73,450		499,654	400,000	100,000
Fair value of shares			$ 2.9		$ 12.6	$ 12	$ 14.3
Restricted stock | Minimum
Incentive award plan
Vesting period					3 years
Restricted stock | Maximum
Incentive award plan
Vesting period					4 years
Performance conditions | Executives
Incentive award plan
Shares subject to conditions (in shares)				24,050
Performance conditions | CEO
Incentive award plan
Granted (in shares)	105,000
Shares subject to conditions (in shares)				105,000

Stock option and award plan_ 64

Stock option and award plan: Incentive award plan fair value assumptions (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Incentive award plan
Weighted-average per share grant date fair value (in dollars per share)	$ 7.06	$ 6.23	$ 6.29
Assumptions used for determining the fair value of options granted
Dividend yield (as a percent)	4.10%	3.70%	3.80%
Expected volatility (as a percent)	27.10%	30.80%	32.50%
Risk-free interest rate (as a percent)	2.00%	1.40%	1.50%
Expected life of the option term (in years)	4 years 6 months	4 years 7 months 6 days	4 years 7 months 6 days

Stock option and award plan_ 65

Stock option and award plan: Incentive award plan - activity (Details) - Stock options $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Stock option activity
Outstanding at the beginning of the period (in shares) | shares	183,322
Granted (in shares) | shares	81,236
Cancelled and expired (in shares) | shares	(35,340)
Exercised (in shares) | shares	(39,289)
Outstanding at the end of the period (in shares) | shares	189,929
Exercisable at the end of the period (in shares) | shares	109,084
Expected to vest (in shares) | shares	168,762
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 32.35
Granted (in dollars per share) | $ / shares	43.93
Cancelled and expired (in dollars per share) | $ / shares	38.72
Exercised (in dollars per share) | $ / shares	31.12
Outstanding at the end of the period (in dollars per share) | $ / shares	36.37
Exercisable at the end of the period (in dollars per share) | $ / shares	32.85
Expected to vest (in dollars per share) | $ / shares	$ 35.63
Stock option activity parenthetical
Exercised - intrinsic value | $	$ 0.5
Exercised - cash received | $	1.2
Outstanding end of period - intrinsic value | $	$ 1.8
Outstanding - weighted-average term	7 years 6 months
Exercisable - intrinsic value | $	$ 1.4
Exercisable - weighted average term	6 years 4 months 24 days
Expected to vest - intrinsic value | $	$ 1.7
Expected to vest - weighted average term	7 years 3 months 18 days

Stock option and award plan_ No

Stock option and award plan: Non-vested restricted stock (Details) - Restricted stock - $ / shares	1 Months Ended	12 Months Ended
	May 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of shares
Non-vested at the beginning of the period (in shares)		908,761
Granted (in shares)	73,450	499,654	400,000	100,000
Vested (in shares)		(286,083)
Forfeited (in shares)		(10,181)
Non-vested at the end of the period (in shares)		1,112,151	908,761
Weighted-Average Grant Date Fair Value
Non-vested at the beginning of the period (in dollars per share)		$ 35.94
Granted (in dollars per share)		40.52	$ 38.87	$ 33.19
Vested (in dollars per share)		35.35
Forfeited (in dollars per share)		39.88
Non-vested at the end of the period (in dollars per share)		$ 38.11	$ 35.94

Stock option and award plan_ 67

Stock option and award plan: Incentive award plan, additional information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Incentive Award Plan, additional information
Equity-based compensation expense		$ 13.3	$ 10.7	$ 11.5
Income tax benefit related to stock options and restricted stock		2.5	2.8	1.8
Capitalized compensation expense		1.2	$ 1.2	$ 1
Total unrecognized compensation cost		$ 26.4
Weighted-average period to recognize unrecognized compensation cost		2 years 1 month 6 days
Restricted stock
Incentive Award Plan, additional information
Granted (in dollars per share)		$ 40.52	$ 38.87	$ 33.19
Granted (in shares)	73,450	499,654	400,000	100,000
Fair value of shares	$ 2.9	$ 12.6	$ 12	$ 14.3

Related party transactions_ (De

Related party transactions: (Details) - Lease $ in Millions	May 10, 2015Owner	Apr. 30, 2015USD ($)Owner	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Office lease
Number of owners | Owner	2	2
Notice period for cancellation of lease	60 days	60 days
Fixed annual rent		$ 1
Lease term (in years)		5 years
Payment for rent and related costs (in dollars)			$ 1.6	$ 1.7	$ 1.2
CEO
Office lease
Ownership percentage	51.00%	51.00%
Chief Executive Officer's wife
Office lease
Ownership percentage	49.00%	49.00%

Geographic information_ (Detail

Geographic information: (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Geographic information
Number of operating segments | segment									1
Service revenue	$ 125,226	$ 122,969	$ 119,777	$ 117,203	$ 115,596	$ 113,057	$ 109,955	$ 108,291	$ 485,175	$ 446,900	$ 404,234
Long lived assets, net	381,306				361,665				381,306	361,665	360,163
North America
Geographic information
Service revenue									402,194	372,810	332,814
Long lived assets, net	282,112				285,651				282,112	285,651	285,187
Europe
Geographic information
Service revenue									82,981	74,090	71,420
Long lived assets, net	$ 99,194				$ 76,014				$ 99,194	$ 76,014	$ 74,976

Quarterly financial informati70

Quarterly financial information (unaudited): (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly financial information (unaudited):
Service revenue	$ 125,226	$ 122,969	$ 119,777	$ 117,203	$ 115,596	$ 113,057	$ 109,955	$ 108,291	$ 485,175	$ 446,900	$ 404,234
Network operations, including equity-based compensation expense	53,918	53,584	51,115	50,662	50,089	48,827	47,872	47,277	209,278	194,066	174,510
Gains on equipment transactions	319	397	1,023	2,124	667	687	4,439	1,946	3,862	7,739	5,443
Operating income	20,534	17,720	19,000	18,666	14,795	16,063	17,511	15,675	75,918	64,042	53,036
Net income (loss)	$ (6,227)	$ 3,650	$ 4,317	$ 4,136	$ 3,892	$ 3,459	$ 4,224	$ 3,354	$ 5,876	$ 14,929	$ 4,896
Net income (loss) per common share-basic and diluted	$ (0.14)	$ 0.08	$ 0.10	$ 0.09	$ 0.09	$ 0.08	$ 0.09	$ 0.08
Weighted-average number of common shares-basic	44,844,469	44,767,163	44,717,372	44,649,645	44,577,826	44,574,583	44,491,899	44,402,640	44,855,263	44,641,805	44,888,723
Weighted-average number of common shares-diluted	44,844,469	45,118,607	44,988,655	44,917,014	44,803,782	44,816,860	44,757,494	44,571,937	45,184,203	44,873,030	45,159,489

Subsequent Events_ (Details)

Subsequent Events: (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 26, 2018	Feb. 21, 2018	Feb. 28, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent events
Expected value of dividend to be paid					$ 81,657	$ 68,210	$ 66,314
Stock options
Subsequent events
Granted (in shares)				470,404
Fair value of shares				$ 19,000
Performance conditions | CEO
Subsequent events
Granted (in shares)			105,000
Subsequent Event
Subsequent events
Quarterly dividend payment approved (per share)		$ 0.50
Subsequent Event | Stock options
Subsequent events
Granted (in shares)			300,000
Fair value of shares			$ 14,100
Subsequent Event | Performance conditions | Executives
Subsequent events
Granted (in shares)			24,050
Subsequent Event | Expected
Subsequent events
Expected value of dividend to be paid	$ 22,400

Schedule II VALUATION AND QUA72

Schedule II VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in valuation and qualifying accounts
Bad debt expense, net of recoveries	$ 3,700	$ 2,800	$ 3,300
Allowance for doubtful service accounts receivable (deducted from accounts receivable)
Movement in valuation and qualifying accounts
Balance at Beginning of Period	1,734	1,757	1,707
Charged to Costs and Expenses	4,835	3,840	4,746
Deductions	(5,070)	(3,863)	(4,696)
Balance at End of Period	1,499	1,734	1,757
Deferred tax valuation allowance
Movement in valuation and qualifying accounts
Balance at Beginning of Period	110,194	113,392	245,104
Charged to Costs and Expenses	20,102	3,102	1,058
Deductions	(623)	(6,300)	(132,770)
Balance at End of Period	$ 129,673	$ 110,194	$ 113,392