NxStage Medical 10-Q 7 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 01, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Trading Symbol	NXTM
Entity Registrant Name	NxStage Medical, Inc.
Entity Central Index Key	1,333,170
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		65,577,459

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 76,287	$ 64,928
Accounts receivable, net	34,506	31,625
Inventory	50,318	49,212
Prepaid expenses and other current assets	8,310	7,609
Total current assets	169,421	153,374
Property and equipment, net	55,484	60,262
Field equipment, net	23,848	24,264
Deferred cost of revenues	32,493	31,410
Intangible assets, net	6,639	7,660
Goodwill	42,748	42,748
Other assets	6,203	5,911
Total assets	336,836	325,629
Current liabilities:
Accounts payable	14,958	14,785
Accrued expenses	31,147	27,985
Current portion of long-term debt	99	101
Other current liabilities	4,185	4,559
Total current liabilities	50,389	47,430
Deferred revenues	47,559	46,874
Long-term debt	454	520
Other long-term liabilities	17,164	17,824
Total liabilities	115,566	112,648
Commitments and contingencies (Note 10)
Noncontrolling interests subject to put provisions	(197)	(165)
Stockholders’ equity:
Undesignated preferred stock: par value $0.001 per share, 5,000,000 shares authorized; no shares issued and outstanding as of June 30, 2018 and December 31, 2017	0	0
Common stock: par value $0.001 per share, 100,000,000 shares authorized; 67,711,012 and 67,341,819 shares issued as of June 30 ,2018 and December 31, 2017, respectively	68	67
Additional paid-in capital	665,186	657,640
Accumulated deficit	(419,680)	(421,593)
Accumulated other comprehensive loss	(4,578)	(3,673)
Treasury stock, at cost: 1,083,013 and 1,046,870 shares as of June 30, 2018 and December 31, 2017, respectively	(20,170)	(19,283)
Total NxStage Medical, Inc. stockholders' equity	220,826	213,158
Noncontrolling interests not subject to put provisions	641	(12)
Total stockholders' equity	221,467	213,146
Total liabilities and stockholders’ equity	$ 336,836	$ 325,629

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Undesignated preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Undesignated preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Undesignated preferred stock, shares issued (in shares)	0	0
Undesignated preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	67,711,012	67,341,819
Treasury stock, shares (in shares)	1,083,013	1,046,870

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Revenues	$ 106,970	$ 96,216	$ 214,268	$ 193,045
Cost of revenues	61,023	55,050	122,156	110,689
Gross profit	45,947	41,166	92,112	82,356
Operating expenses:
Selling and marketing	18,131	16,841	36,186	33,611
Research and development	10,593	9,027	20,031	18,535
Distribution	8,561	7,686	17,903	15,329
General and administrative	9,751	9,668	20,211	18,618
Total operating expenses	47,036	43,222	94,331	86,093
Loss from operations	(1,089)	(2,056)	(2,219)	(3,737)
Other expense:
Interest expense, net	(88)	(224)	(197)	(427)
Other expense, net	(672)	(321)	(967)	(591)
Total other expense	(760)	(545)	(1,164)	(1,018)
Net loss before income taxes	(1,849)	(2,601)	(3,383)	(4,755)
Provision for (benefit from) income taxes	372	(22)	636	(635)
Net loss	(2,221)	(2,579)	(4,019)	(4,120)
Less: Net income (loss) attributable to noncontrolling interests	368	(490)	29	(842)
Net loss attributable to NxStage Medical, Inc.	$ (2,589)	$ (2,089)	$ (4,048)	$ (3,278)
Net loss per share, basic and diluted (in dollars per share)	$ (0.04)	$ (0.03)	$ (0.06)	$ (0.05)
Weighted-average shares outstanding, basic and diluted (in shares)	66,552	65,821	66,552	65,544
Other comprehensive (loss) income:
Unrealized (loss) income on derivative instruments, net of income taxes	$ (822)	$ 853	$ (361)	$ 3,037
Other (loss) income	(1,242)	841	(544)	1,562
Total other comprehensive (loss) income	(2,064)	1,694	(905)	4,599
Total comprehensive (loss) income	(4,285)	(885)	(4,924)	479
Less: Comprehensive income (loss) attributable to noncontrolling interests	368	(490)	29	(842)
Total comprehensive (loss) income attributable to NxStage Medical, Inc.	$ (4,653)	$ (395)	$ (4,953)	$ 1,321

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net loss	$ (4,019)	$ (4,120)
Adjustments to reconcile net loss to net cash flow from operating activities:
Depreciation and amortization	16,946	16,838
Stock-based compensation	4,977	5,324
Other	1,214	(211)
Changes in operating assets and liabilities:
Accounts receivable	1,379	607
Inventory	(12,744)	(15,160)
Prepaid expenses and other assets	773	(272)
Accounts payable	363	401
Accrued expenses and other liabilities	3,256	(2,159)
Deferred revenues	741	(1,446)
Net cash provided by (used in) operating activities	12,886	(198)
Cash flows from investing activities:
Purchases of property and equipment	(2,241)	(4,933)
Net cash used in investing activities	(2,241)	(4,933)
Cash flows from financing activities:
Issuance of shares under stock incentive plans, net of payroll taxes paid	1,650	8,121
Repayments on loans and lines of credit	(50)	(108)
Repayments on capital leases	(781)	(666)
Net cash provided by financing activities	819	7,347
Foreign exchange effect on cash and cash equivalents	(105)	991
Increase in cash and cash equivalents	11,359	3,207
Cash and cash equivalents, beginning of period	64,928	59,632
Cash and cash equivalents, end of period	$ 76,287	$ 62,839

Nature of Operations, Proposed

Nature of Operations, Proposed Merger, Basis of Presentation and Principles of Consolidation	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Nature of Operations, Proposed Merger Agreement, Basis of Presentation and Principles of Consolidation	Nature of Operations, Proposed Merger, Basis of Presentation and Principles of Consolidation Nature of Operations We are a medical technology company that develops, manufactures, markets and provides innovative products and services for patients suffering from chronic or acute kidney failure. Our primary product, the System One, was designed to satisfy an unmet clinical need for a system capable of delivering the therapeutic flexibility and clinical benefits of traditional dialysis machines in a smaller, portable, easy-to-use form that can be used by healthcare professionals and trained lay users alike in a variety of settings, including patient homes and home-like settings, including skilled nursing facilities, as well as more traditional care settings such as hospitals and dialysis centers. Given its design, the System One is particularly well-suited for home hemodialysis and a range of dialysis therapies that are more practical to deliver in the home setting, including more frequent hemodialysis and nocturnal hemodialysis. Clinical literature suggests such therapies provide patients better clinical outcomes and improved quality of life. In addition to the System One, we provide patients with our PureFlow SL accessory which prepares on-site premixed dialysate fluid in the patient's home using ordinary tap water and dialysate concentrate. We also operate a small number of NxStage Kidney Care dialysis centers, independently and in some instances as joint ventures, that treat end-stage renal disease (ESRD) patients directly. These centers provide us with the opportunity to innovate and foster new care delivery models to advance the standard of renal care across other markets. At these centers, we offer a range of treatment options, including home hemodialysis, peritoneal dialysis and flexible in-center hemodialysis. We are headquartered in Lawrence, Massachusetts, with manufacturing facilities in Mexico, Germany and Italy. Through our international network of affiliates and distribution partners, patients in over 21 countries have been treated with our products. Proposed Merger On August 7, 2017, we entered into an Agreement and Plan of Merger (Merger Agreement) with Fresenius Medical Care Holdings, Inc. (Fresenius), pursuant to which we will merge with a wholly-owned subsidiary of Fresenius (Merger), subject to certain conditions. At the closing of the Merger, all outstanding shares of our common stock (except those held by us, Fresenius or its wholly-owned subsidiaries or any stockholders properly exercising their appraisal rights under the General Corporation Law of the State of Delaware) would be converted into the right to receive $30.00 per share in cash, subject to any applicable tax withholdings. The closing of the Merger is conditioned, among other things, on receipt of regulatory approval from the U.S. Federal Trade Commission (FTC) and the expiration of applicable waiting periods, or extensions thereof, under the Hart-Scott-Rodino Act of 1976, as amended (HSR Act). Pursuant to the HSR Act, we and Fresenius each submitted pre-merger notification filings to the FTC and Department of Justice, Antitrust Division. On October 18, 2017, we and Fresenius each received a Request for Additional Information and Documentary Material (also known as a Second Request) from the FTC. The effect of the Second Request is to extend the waiting period imposed by the HSR Act until 30 days after Fresenius and we have substantially complied with the Second Request, unless that period is terminated sooner by the FTC. By agreement with the FTC, the parties may voluntarily extend the time for closing beyond the expiration of the HSR Act waiting period. The parties continue to work to obtain FTC approval of the proposed transaction. On October 27, 2017, the stockholders of NxStage Medical, Inc. voted to approve the Merger Agreement. In addition, the Merger has cleared antitrust review in Germany. See “Risk Factors” in Part I Item 1A of our 2017 Annual Report (as defined below) for additional information. In an effort to advance the process of obtaining FTC clearance of the proposed Merger under the HSR Act, on July 10, 2018 we entered into an agreement to sell our bloodlines business operated under the Medisystems name to B. Braun Medical Inc. Consummation of that transaction is subject to (1) FTC approval of that transaction, (2) the closing of the Merger, (3) and other customary conditions. The original end date for our Merger Agreement with Fresenius (End Date) was August 7, 2018. Fresenius had the option to extend the End Date for an additional 90 days to obtain required antitrust clearances. On July 30, 2018, Fresenius exercised this right, extending the End Date of the Merger Agreement from August 7, 2018 to November 5, 2018. The Merger Agreement may be terminated by us or Fresenius if the Merger is not closed by November 5, 2018, although Fresenius may extend the End Date for an additional 90 days under certain circumstances in order to obtain required antitrust clearances. The Merger Agreement generally requires each party to use its reasonable best efforts to obtain all consents and clearances required under any antitrust law, except that Fresenius is not required (i) to litigate against a governmental entity or (ii) to divest or to take any other actions with respect to any assets or business of Fresenius, its subsidiaries or the Company, other than, if necessary to obtain antitrust clearances, with respect to certain Company assets. Fresenius is required to pay us a termination fee of $100 million (the Reverse Termination Fee) if the Merger Agreement is terminated by us or Fresenius (i) if the End Date and any applicable extension has passed or (ii) if a court or other governmental entity issues a final, nonappealable order or takes any other actions that permanently prohibits the Merger or makes closing the Merger illegal (in each case because approval under applicable antitrust laws remains the only unsatisfied closing condition). We would be required to pay Fresenius a termination fee of $60 million (the Termination Fee) if all of the following conditions were applicable: (i) the Merger Agreement is terminated because the End Date has passed or we have breached a representation or warranty, (ii) an alternative acquisition proposal has been publicly made and not publicly withdrawn at least ten days prior to the termination, and (iii) within 12 months following such termination, we enter into an alternative acquisition agreement or an alternative acquisition is consummated. Nonetheless, we will not be required to pay the Termination Fee if the Merger Agreement is terminated due to failure to obtain required antitrust approvals by the End Date and Fresenius is required to pay the Reverse Termination Fee. The Merger Agreement includes customary representations, warranties and covenants. Pursuant to the Merger Agreement, we agreed to use commercially reasonable efforts to operate our business in all material respects in the ordinary course until closing. Basis of Presentation The accompanying condensed consolidated financial statements as of June 30, 2018 and December 31, 2017 and for the three and six months ended June 30, 2018 and 2017 , and related notes, are unaudited but, in the opinion of our management, include all adjustments, consisting of normal recurring adjustments, that are necessary for fair statement of the interim periods presented. Our unaudited condensed consolidated financial statements have been prepared following the requirements of the Securities and Exchange Commission (SEC) for interim reporting. As permitted under these rules, we have condensed or omitted certain footnotes and other financial information that are normally required by U.S. generally accepted accounting principles (GAAP). Our accounting policies are described in the notes to the consolidated financial statements in our Annual Report on Form 10-K for the year ended December 31, 2017 ( 2017 Annual Report) and updated, as necessary, in this Quarterly Report on Form 10-Q (Quarterly Report). Operating results for any interim period are not necessarily indicative of results for the entire year or future periods. The December 31, 2017 condensed consolidated balance sheet contained herein was derived from audited financial statements, but does not include all disclosures that would be required for audited financial statements under GAAP. For further information, refer to the consolidated financial statements and footnotes thereto included in our 2017 Annual Report. We adopted Accounting Standards Update (ASU) No. 2014-9: “Revenue from Contracts with Customers” (ASC 606) with a date of initial application of January 1, 2018. We applied ASC 606 using the cumulative effect method, i.e., by recognizing the cumulative effect of initially applying ASC 606 as an adjustment to the opening balance of equity at January 1, 2018. Therefore, the comparative information has not been adjusted and continues to be reported under ASC 605. The details of the significant changes and quantitative impact of the changes are outlined in Note 2. The preparation of our condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure 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 could differ from those estimates. Such financial statements reflect all adjustments that, in the opinion of management, are necessary for a fair presentation of the results of the periods presented. All such adjustments are of a normal recurring nature. Principles of Consolidation Our condensed consolidated financial statements include the accounts of NxStage Medical, Inc. and our wholly-owned subsidiaries and other entities in which we maintain a majority voting interests or for which we maintain effective control, including variable interest entities ("VIEs") for which we are deemed the primary beneficiary. All significant intercompany balances and transactions have been eliminated. Noncontrolling interests represent the proportionate equity interests in the consolidated entities that are not wholly owned by us. Noncontrolling interests of acquired entities are recognized at their initial fair value.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Revenue Recognition We recognize revenue from product sales and services when earned through fulfillment of our performance obligations. The amount of revenue recognized is based on the total consideration that we ultimately expect to collect relative to the good or service provided. We estimate the standalone selling price for an individual performance obligation based on consideration of both industry and Company-specific factors, including the profit margin for similar products, the cost to produce the deliverable and the anticipated margin on that deliverable and the characteristics of the varying markets in which the deliverable is sold. Any tax assessed by a governmental authority that is incurred as a result of a revenue transaction (e.g. sales tax) is excluded from revenues and reported on a net basis. In general, we do not have any significant extended payment terms as payment is received at or shortly after the point of sale. The expected costs associated with our standard product warranties continue to be recognized as expense when the products are sold. When shipping and handling activities are performed after the transfer of control to the customer (e.g., when control transfers prior to delivery), they are considered as fulfillment activities, and accordingly, the costs are accrued for when the related revenue is recognized. System One Segment We derive revenue in the home market primarily from sales of the System One hardware and sales of disposable products. We enter into arrangements with customers that may include multiple elements including equipment lease transactions pursuant to the depot service model described below or equipment sales with no post-delivery obligations other than standard warranty obligations, disposable product sales and services. The transaction price is allocated to the elements including allocation to the lease and non-lease elements of the arrangement, where applicable, based on their relative standalone selling price and recognized pursuant to the applicable guidance. System One hardware sales to dialysis clinic customers in the home market are made under the depot service model whereby equipment requiring service is picked up and a replacement device is shipped to the site of care. Accordingly, we recognize upfront fees received from equipment transactions as revenue on a straight-line basis over the term of our remaining service obligation, which generally range between 5 and 7 years, and direct costs relating to the delivered equipment are classified in deferred cost of revenues and amortized over the same expected period as the related revenue. Disposable products sales are recognized in accordance with the contract terms. We also offer a month-to-month System One hardware rental arrangements. Under these arrangements, revenue is recognized on a monthly basis in accordance with agreed upon arrangements with the customers. Our sales arrangements with our international distributors are structured as direct product sales and have no significant post-delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. In the critical care market, we structure sales of the System One and disposable products as direct product sales and have no significant post-delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Certain of these arrangements provide for training, technical support and equipment service to our customers. We recognize training and technical support revenue when the related services are performed and our performance obligations are satisfied. In the case of equipment service contracts entered into after the initial standard warranty period, the service contract revenue is recognized ratably over the service period. Some of our contracts with customers in the System One segment contain contractually determined volume discounts offered to similar classes of customers. In addition, in many agreements we offer rebates and discounts for early payment which result in the ultimate payment being variable. The variable consideration paid by the customer is estimated and recognized when we satisfy our performance obligation (generally upon delivery) to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized to date will not occur. We are able to reliably estimate the amount of rebates and discounts and record them as a reduction to revenue and accounts receivable at the time of sale. In-Center Segment Our In-Center segment sales are structured as direct product sales primarily through distributors, and we have no significant post-delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Some of our distribution contracts for the In-Center segment contain rebates and discounts for early payment which results in the ultimate payment being variable. The variable fee paid by the distributor is estimated and recognized when we satisfy our performance obligation (generally upon delivery to the distributor) to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized to date will not occur. We are able to reliably estimate the amount of rebates/discounts and record them as a reduction to revenue and trade accounts receivable at the time of sale. Services Segment Revenues in our Services segment are derived from dialysis care services provided to patients at our NxStage Kidney Care dialysis centers. Revenues are recognized in the period in which services are provided. For revenues associated with Medicare, Medicaid or commercial insurers with which we have formal agreements, revenue is recognized based on contractual rates or rates established by statute or regulation in the case of Medicare and Medicaid. For certain classes of payors, for example non-contracted commercial health insurance payors and amounts due from patients (including co-pay and deductible amounts), revenue is recognized based on our estimate of the consideration that will be ultimately received from the payor which results in the ultimate payment being variable. The variable fee is estimated using historical collections experience with similar classes of payors and recognized when we satisfy our performance obligation (when services are provided) to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized to date will not occur. Overall, these estimates reflect the Company’s best estimates of the amount of consideration to which it is entitled from these customers. The amount of variable consideration which is included in the transaction price may be constrained, and is included in the sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from our estimates. If actual results in the future vary from our estimates, we adjust these estimates, which would affect revenues and earnings in the period such variances become known. Such changes, if material, will be disclosed in the period such variances become known. Other Other revenues relate to the manufacturing of dialyzers for sale to Asahi Kasei Kuraray Medical Co. (Asahi). Sales to Asahi are structured as direct product sales and we have no significant post-delivery obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Costs to Obtain or Fulfill a Contract We capitalize commission fees as costs of obtaining a contract, when they are incremental and if they are expected to be recovered, and amortize them consistently with the pattern of transfer of the good to which the asset relates. If the expected amortization period is one year or less, the commission fee is expensed when incurred. Direct costs related to the delivered equipment within the System One home market are capitalized as deferred cost of revenues and amortized over the same expected period as the related revenue. Concentration of Credit Risk Concentration of credit risk with respect to accounts receivable is primarily limited to certain customers to whom we make substantial sales. No customer represented more than 10% of accounts receivable at June 30, 2018 or December 31, 2017 . Warranty Costs We accrue estimated costs that we may incur under our product warranty programs at the time the product revenue is recognized, based on contractual rights and historical experience. Warranty expense is included in cost of revenues in the condensed consolidated statements of comprehensive loss. The following is a rollforward of our warranty accrual (in thousands): Balance at December 31, 2017 $ 293 Provision 173 Usage (224 ) Balance at June 30, 2018 $ 242 Intangibles and Other Long-Lived Assets Intangible assets are carried at cost less accumulated amortization. For assets with determinable useful lives, amortization is recognized using the straight-line method over the estimated economic lives of the respective intangible assets. Long-lived assets, including intangible assets, are evaluated for recoverability whenever events or circumstances indicate that their carrying value may not be recoverable. Recoverability of long-lived assets is assessed at the lowest level for which discrete cash flows are available and is measured by comparing the asset group’s carrying value to its expected non-discounted future cash flows. If the sum of the expected non-discounted future cash flows is less than the carrying amount of the long-lived assets, an impairment loss is recognized for excess of the carrying amount of the asset group over its fair value. In the second quarter of 2018 , events and circumstances have indicated that certain long-lived tangible assets in the Services segment may not be recoverable. Therefore, a recoverability test was performed at the center level by comparing the carrying value of each center to its estimated future undiscounted cash flows, within the initial lease term (which is the equivalent to the depreciable life of the centers' most significant asset, its leasehold improvements). As of June 30, 2018 , our expected non-discounted future cash flows for the majority of our centers indicated such carrying amounts were expected to be recovered. We recorded an impairment charge during the second quarter of 2018 of $0.1 million in cost of revenue to write-down certain center level assets within our Services segment. Our expected non-discounted future cash flows used in our impairment testing are based upon cash flow projections and, if appropriate, include assumed proceeds upon sale of the asset group at the end of the cash flow period. We believe our procedures for developing cash flow projections, including the estimated sales proceeds, are reasonable and consistent with current market conditions for each of the dates when impairment testing has been performed. Developing cash flow projections requires significant estimates and judgment. Among other things, slower than expected patient ramp or lower than expected reimbursement rates would negatively impact our cash flow projections in the near term. Fair value of the asset group was estimated using a discounted cash flow approach. Estimating fair value requires significant judgment in the selection of the valuation technique and assumptions used in developing cash flow projections, growth rates and discount rates. Our assumptions are based on our best estimates, using appropriate and customary market participant assumptions. Any adverse changes in certain valuation assumptions could result in the need to record additional impairment to write down all or a portion the centers’ remaining asset carrying value. We had $11.5 million of long-lived assets at our Services segment at June 30, 2018 . It is reasonably possible that our cash flow projections may change in the near term resulting in the need to record an impairment charge for at least some portion of these assets. Goodwill We test goodwill for impairment during the fourth quarter, or more frequently when events or changes in circumstances indicate that the goodwill might be impaired. This test includes first a qualitative assessment and then, if necessary, a quantitative assessment to determine if the fair value of a reporting unit is less than its carrying amount. Our System One, In-center and Services reporting units contain goodwill of $41.1 million , $0.5 million and $1.1 million , respectively. Factors considered in the qualitative assessment include, but are not limited to, both macroeconomic conditions and entity-specific conditions. For the quantitative assessment the reporting unit's fair value is estimated using a discounted cash flow or other fair value measurement. During 2017 and 2016 we utilized the qualitative assessment to assess the fair value of our System One and In-center reporting units and concluded that it was more likely than not that the fair value of our reporting units was greater than their carrying value. During 2017 , we also utilized the qualitative assessment to assess the fair value of our Services reporting unit and concluded that it was more likely than not that the fair value of the reporting unit was greater than its carrying value. During 2016, for our Services reporting unit, we utilized the quantitative assessment noting that the fair value of the reporting unit exceeds its carrying value, indicating that goodwill was not impaired. We estimated the fair value of our Services reporting unit using a discounted cash flow approach. Estimating the fair value of our Services reporting unit requires significant judgment in the selection of the valuation technique and assumptions used in cash flow projections, growth rates and discount rates. Our assumptions are based on our best estimates, using appropriate and customary market participant assumptions. There have been no events or changes in circumstances since the date of our last goodwill impairment tests that would indicate it is more likely than not that the fair value of our reporting units is less than their carrying value. Developing cash flow projections involves significant judgment with respect to patient additions and reimbursement rates, operating income, capital expenditures and changes in working capital. Reductions in our cash flow projections due to slower than expected patient ramp or lower than expected reimbursement rates, among other things, or adverse changes in certain valuation assumptions or changes in the reporting units net assets could result in a goodwill impairment charge of up to $1.1 million in our Services reporting unit in the future. Recent Accounting Pronouncements Recently Implemented Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued ASU No. 2014-9: “Revenue from Contracts with Customers” (ASC 606). The standard provides that revenue should be recognized when an entity transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In addition, the standard requires disclosure of the nature, amount, timing and uncertainty of revenues and cash flow arising from contracts with customers. The FASB has issued several amendments and updates to the new revenue standard, including how an entity should identify performance obligations. As amended, the new guidance was effective for us beginning January 1, 2018. We adopted ASC 606 using the modified retrospective method approach as of January 1, 2018. This approach was applied to all contracts not completed as of January 1, 2018. We recognized the cumulative effect of initially applying the new revenue standard as an adjustment to the opening balance of retained earnings. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. See above in Note 2 for discussion of our updated Revenue Recognition policy. We do not expect the adoption of the new revenue standard to have a material impact to our net income on an ongoing basis. The adoption of ASC 606 impacted the timing of revenue recognition for our Services segment and resulted in enhanced footnote disclosures related to customer contracts as included in Note 3 to these condensed consolidated financial statements. It also modified the accounting for commissions fees as it requires such incremental and recoverable costs to be capitalized and amortized over the estimated life of the asset. Previously, these costs were expensed as incurred. The cumulative effect of the changes made to our condensed consolidated balance sheet for the adoption of ASC 606 was as follows (in thousands): As Reported Adjustment due to ASC 606 December 31, 2017 January 1, 2018 ASSETS Accounts receivable, net $ 31,625 $ 4,419 $ 36,044 Prepaid expenses and other current assets 7,609 1,895 9,504 Deferred cost of revenues 31,410 (139 ) 31,271 Other assets 5,911 379 6,290 LIABILITIES AND STOCKHOLDERS’ EQUITY Noncontrolling interests subject to put provisions (165 ) 49 (116 ) Accumulated deficit (421,593 ) 5,961 (415,632 ) Noncontrolling interests not subject to put provisions (12 ) 544 532 In accordance with the new revenue standard requirements, the disclosure of the impact of adoption on our condensed consolidated statement of comprehensive loss for the three and six months ended June 30, 2018 was as follows (in thousands): Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 As Reported Balance without adoption of ASC 606 Effect of Change As Reported Adjustment to ASC 606 Effect of Change Revenues $ 106,970 $ 107,293 $ (323 ) $ 214,268 $ 215,727 $ (1,459 ) Cost of revenues 61,023 61,068 (45 ) 122,156 122,262 (106 ) Selling and marketing 18,131 18,196 (65 ) 36,186 36,351 (165 ) In accordance with the new revenue standard requirements, the disclosure of the impact of adoption on our condensed consolidated balance sheet at June 30, 2018 was as follows (in thousands): June 30, 2018 ASSETS As Reported Balance without adoption of ASC 606 Effect of Change Accounts receivable, net $ 34,506 $ 31,269 $ 3,237 Prepaid expenses and other current assets 8,310 6,269 2,041 Deferred cost of revenues 32,493 32,525 (32 ) Other assets 6,203 5,805 398 LIABILITIES AND STOCKHOLDERS’ EQUITY Noncontrolling interests subject to put provisions $ (197 ) $ (227 ) $ 30 Accumulated deficit (419,680 ) (425,268 ) 5,588 Noncontrolling interests not subject to put provisions 641 619 22 Accumulated other comprehensive loss (4,578 ) (4,582 ) 4 The impacts noted above are primarily attributable to the change in the timing of revenue recognition for our Services segment as the standard requires revenues to be estimated and recognized upon transfer of the promised goods and services and accounting for capitalization of certain commissions. In January 2016, the FASB issued ASU No. 2016-01: “Financial Instruments-Overall: Recognition and Measurement of Financial Assets and Financial Liabilities” which impacts the recognition, measurement, presentation and disclosure of financial assets and financial liabilities. Among other things, the standard generally requires all equity investments (except those accounted for under the equity method and those that result in consolidation of the investee) be measured at fair value through earnings. For those equity instruments that do not have readily determinable fair values, the standard permits the application of a measurement alternative using the cost of the investment, less any impairments, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer with such changes recognized in net income. The new guidance was effective for us beginning January 1, 2018. We have made this measurement alternative policy election for our equity investments without readily determinable fair values. The adoption of this standard did not have an impact on our financial position or results of operation. Recent Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02: "Accounting for Leases" which amends the existing accounting standards for leases. The new standard requires lessees to record a right-of-use asset and a corresponding lease liability on the balance sheet for all leases with terms longer than twelve months. For lessees, leases will continue to be classified as either operating or financing in the income statement. This ASU is required to be applied with a modified retrospective approach which gives the option of applying the new lease requirements as of the effective date with enhanced disclosure requirements for comparative periods presented under the current guidance or applying the new standard at the beginning of the earliest comparative period presented. The new guidance is effective for us beginning January 1, 2019 and early adoption is permitted. We are evaluating the method of adoption and the potential impact of the standard on our consolidated financial statements and related disclosures and are comparing our current policies and practices to the requirements of the standard. We have developed a project plan to develop processes and tools in order to adopt the standard on January 1, 2019. We have periodically briefed our Audit Committee on our progress made towards adoption. In August 2017, the FASB issued ASU 2017-12: "Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities" which amends the hedge accounting recognition and presentation requirements. The update is intended to more closely align hedge accounting with companies’ risk management strategies, simplify the application of hedge accounting and increase transparency as to the scope and results of hedge programs. The update is effective for us beginning January 1, 2019, with early adoption permitted. We are currently evaluating the potential impact this update will have on our financial statements.

Revenues

Revenues	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenues	Revenues The following table disaggregates our revenues by market (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2018 System One segment Home $ 61,755 120,434 Critical Care 22,325 46,533 Total System One segment 84,080 166,967 In-Center segment 16,389 33,746 Other 2,522 5,342 Products subtotal 102,991 206,055 Services segment 5,184 10,603 Elimination of intersegment revenues (1,205 ) (2,390 ) Total $ 106,970 $ 214,268 For the three and six months ended June 30, 2018 , revenue recognized from performance obligations related to prior periods, including changes to variable consideration estimates, was not material. Capitalized commission fees are amortized consistently with the pattern of transfer of the good to which the asset relates which is approximately 21 months. Capitalized commission fees were $2.2 million and $2.0 million as of June 30, 2018 and January 1, 2018, respectively, and are included in prepaid expenses and other current assets and other assets on our condensed consolidated balance sheet. During the six months ended June 30, 2018 , we recorded $1.2 million of amortization expense related to capitalized commissions, which is included in sales and marketing expense, and there was no impairment loss in relation to the costs capitalized. Long-term deferred revenues primary relate to sales of System One hardware to dialysis clinic customers in the home market made under the depot service model which is deemed to be a lease element of the respective home transactions and, to a lesser extent, deferred revenue related to our Dialyzer Production Agreement with Asahi which is recognized in revenues on a straight-line basis over the expected term of the agreement. Other revenue expected to be recognized in future years related to remaining performance obligations, excluding revenue pertaining to contracts that have an original expected duration of one year or less and contracts where revenue is recognized as invoiced, is immaterial.

Inventory

Inventory	6 Months Ended
	Jun. 30, 2018
Inventory Disclosure [Abstract]
Inventory	Inventory Inventory includes material, labor and overhead, and is stated at lower of cost (first-in, first-out) or market (net realizable value). The components of inventory are as follows (in thousands): June 30, December 31, Purchased components $ 14,373 $ 14,947 Work in process 15,275 13,433 Finished goods 20,670 20,832 Total $ 50,318 $ 49,212

Property and Equipment and Fiel

Property and Equipment and Field Equipment	6 Months Ended
	Jun. 30, 2018
Property, Plant and Equipment [Abstract]
Property and Equipment, Field Equipment and Deferred Cost of Revenues	Property and Equipment, Field Equipment and Deferred Cost of Revenues Accumulated depreciation on property and equipment was $62.4 million and $56.8 million at June 30, 2018 and December 31, 2017 , respectively. Accumulated depreciation on field equipment was $53.3 million and $51.6 million at June 30, 2018 and December 31, 2017 , respectively. Accumulated amortization on deferred costs of revenues was $112.8 million and $106.3 million at June 30, 2018 and December 31, 2017 , respectively.

Intangible Assets

Intangible Assets	6 Months Ended
	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	Intangible Assets Accumulated amortization of intangible assets was $28.0 million and $27.0 million at June 30, 2018 and December 31, 2017 , respectively.

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic net loss per share is computed by dividing loss attributable to NxStage Medical, Inc. common stockholders (the numerator) by the weighted-average number of common shares outstanding (the denominator) for the period. The computation of diluted loss per share is similar to basic loss per share, except that the denominator is increased to include the number of additional common shares that would have been outstanding if the potentially dilutive common shares had been issued. The following potential common stock equivalents, as calculated using the treasury stock method, were not included in the computation of diluted net loss per share as their effect would have been anti-dilutive due to the net loss incurred (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Options to purchase common stock 1,102 1,002 1,030 1,166 Unvested restricted stock 160 196 196 260 Total 1,262 1,198 1,226 1,426

Accrued Expenses, Other Current

Accrued Expenses, Other Current Liabilities and Other Long-Term Liabilities	6 Months Ended
	Jun. 30, 2018
Payables and Accruals [Abstract]
Accrued Expenses, Other Current Liabilities and Other Long-Term Liabilities	Accrued Expenses, Other Current Liabilities and Other Long-Term Liabilities The components of accrued expenses are as follows (in thousands): June 30, December 31, Payroll, compensation and related benefits $ 14,825 $ 13,195 Distribution expenses 5,419 4,914 Other 10,903 9,876 Total $ 31,147 $ 27,985 The components of other current liabilities are as follows (in thousands): June 30, December 31, Capital lease obligations $ 2,006 $ 2,131 Deferred revenue, current portion 1,309 1,473 Other 870 955 Total $ 4,185 $ 4,559 The components of other long-term liabilities are as follows (in thousands): June 30, December 31, Capital lease obligations $ 10,908 $ 11,589 Lease incentive obligations 2,591 2,652 Benefit plan obligations 2,031 2,060 Other 1,634 1,523 Total $ 17,164 $ 17,824

Segment Disclosures

Segment Disclosures	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Segment Disclosures	Segment Disclosures We have three reportable business segments: System One, In-Center, and Services. The operating results of NxStage Kidney Care are included in our Services segment. We refer to our System One segment, In-Center segment, and Other category as our products business. Our System One segment includes revenues from sales and rentals of the System One and PureFlow SL dialysate preparation equipment and the sale of disposable products to customers in the home market, including through our NxStage Kidney Care dialysis centers, and critical care market. The home market is devoted to the treatment of ESRD patients in the home or a home-like setting, including skilled nursing facilities, while the critical care market is devoted to the treatment of hospital-based patients with acute kidney failure or fluid overload. Some of our largest customers in the home market provide outsourced renal dialysis services to some of our customers in the critical care market. Sales of product to both markets are made primarily through dedicated sales forces and distributed directly to the customer, or the patient, with certain products sold through distributors. Our In-Center segment includes revenues from the sale of blood tubing sets and needles for hemodialysis primarily for the treatment of ESRD patients at dialysis centers and needles for apheresis. Nearly all In-Center products are sold through national distributors. The remainder of our products business, which is included within the Other category, relates to the manufacturing of dialyzers for sale to Asahi Kasei Kuraray Medical Co., Ltd. (Asahi) and research and development and general and administrative expenses that are excluded from the segment operating performance measures. Our Services segment includes revenues from dialysis services provided to patients at our NxStage Kidney Care dialysis centers. Sales of the System One and related products to our NxStage Kidney Care dialysis centers are included in System One segment revenues, which are then eliminated upon consolidation. The accounting policies of our reportable segments are described in Note 2 to the consolidated financial statements included in our 2017 Annual Report and updated, as necessary, in Note 2 to the condensed consolidated financial statements included in this Quarterly Report. Our chief operating decision maker allocates resources to our business segments and assesses segment performance based on segment profit (loss), which consists of revenues less cost of revenues, selling and marketing and distribution expenses. The following summarizes the operating performance of our reportable segments (in thousands): System One In-Center Other Services Intersegment Elimination Total Three Months Ended June 30, 2018 Revenues from external customers $ 82,875 $ 16,389 $ 2,522 $ 5,184 $ — $ 106,970 Intersegment revenues 1,205 — — — (1,205 ) — Revenues 84,080 16,389 2,522 5,184 (1,205 ) 106,970 Segment profit (loss) 22,765 2,436 (20,458 ) (5,867 ) 35 (1,089 ) Depreciation and amortization 5,829 463 1,077 1,319 (46 ) 8,642 Three Months Ended June 30, 2017 Revenues from external customers $ 74,197 14,326 2,836 4,857 $ — $ 96,216 Intersegment revenues 1,261 — — — (1,261 ) $ — Revenues 75,458 14,326 2,836 4,857 (1,261 ) 96,216 Segment profit (loss) 21,374 1,662 (18,582 ) (6,493 ) (17 ) (2,056 ) Depreciation and amortization 5,428 544 1,092 1,302 5 8,371 Six Months Ended June 30, 2018 Revenues from external customers $ 164,577 $ 33,746 $ 5,342 $ 10,603 $ — $ 214,268 Intersegment revenues 2,390 — — — (2,390 ) — Revenues 166,967 33,746 5,342 10,603 (2,390 ) 214,268 Segment profit (loss) 44,485 4,735 (40,083 ) (11,426 ) 70 (2,219 ) Depreciation and amortization 11,264 951 2,161 2,662 (92 ) 16,946 Six Months Ended June 30, 2017 Revenues from external customers $ 147,471 29,932 5,735 9,907 $ — $ 193,045 Intersegment revenues 2,648 — — — (2,648 ) — Revenues 150,119 29,932 5,735 9,907 (2,648 ) 193,045 Segment profit (loss) 41,222 4,021 (36,843 ) (12,098 ) (39 ) (3,737 ) Depreciation and amortization 11,062 1,069 2,164 2,570 (27 ) 16,838 Substantially all of our revenues are derived from the sale of the System One and related products, which cannot be used with any other dialysis system, and from needles and blood tubing sets in the U.S. The following table summarizes the number of customers who individually make up greater than ten percent of total revenues: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 DaVita 19 % 20 % 19 % 20 % Fresenius 21 % 20 % 20 % 19 % Sales to DaVita HealthCare Partners Inc. (DaVita) and Fresenius are in the System One segment.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Significant commitments and contingencies at June 30, 2018 are consistent with those discussed in Note 10 to the consolidated financial statements in our 2017 Annual Report.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recognized a provision for income taxes during the three and six months ended June 30, 2018 and 2017 related to the profitable operations of certain foreign subsidiaries. In addition, the provision recognized during both periods includes the impact of an allocation of U.S. tax expense between continuing operations and total other comprehensive (loss) income of less than $0.1 million and $0.4 million for the three months ended June 30, 2018 and 2017, respectively, and $0.1 million and $1.3 million for the six months ended June 30, 2018 and 2017, respectively. This allocation has no impact on total comprehensive loss or total stockholders' equity for 2018. However, it did result in a net tax benefit from income taxes in continuing operations of less than $0.1 million and $0.6 million during the three and six months ended June 30, 2017, respectively. In accordance with Staff Accounting Bulletin 118, we recognized provisional tax impacts related to the Tax Cuts and Jobs Act of 2017 (Tax Reform) for the year ended December 31, 2017. Specifically, we remeasured our tax assets at December 31, 2017 based on the new Federal income tax rate of 21%. No additional adjustments were recorded in the current quarter. We are still in the process of completing our evaluation of the impact of the Tax Reform on our financial statements. We will continue to make and refine our calculations as additional analysis is completed and gain a more thorough understanding of the Tax Reform. As of June 30, 2018 , we had a liability for unrecognized tax benefits included in the balance sheet of approximately $0.9 million , including a nominal accrual for interest and penalties of less than $0.1 million . There have been no significant changes to these amounts during the three and six months ended June 30, 2018 .

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation Stock-based Compensation Expense The following table presents stock-based compensation expense included in our condensed consolidated statements of comprehensive loss (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Cost of revenues $ 220 $ 263 $ 471 $ 567 Selling and marketing 749 1,137 1,576 1,993 Research and development 311 334 693 717 General and administrative 1,000 1,016 2,237 2,047 Total $ 2,280 $ 2,750 $ 4,977 $ 5,324 Stock Options and Restricted Stock Units The Company granted no new options during the three and six months ended June 30, 2018 . The Company granted options to purchase 130,430 and 667,878 shares of common stock during the three and six months ended June 30, 2017 , which vest based on continued employment over a period of one to four years. The weighted-average fair value of options granted during the six months ended June 30, 2017 was $9.94 per option. The Company awarded no new restricted stock units during the three and six months ended June 30, 2018 . The Company awarded 21,737 and 154,925 restricted stock units during the three and six months ended June 30, 2017 , which vest based on continued employment over a period of three to four years. The weighted-average fair value of these restricted stock units awarded during the six months ended June 30, 2017 was $27.69 per unit.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity We received 36,143 and 88,939 shares of common stock that were surrendered in payment for the exercise of stock options during the six months ended June 30, 2018 and 2017 , respectively.

Noncontrolling Interest

Noncontrolling Interest	6 Months Ended
	Jun. 30, 2018
Noncontrolling Interest [Abstract]
Noncontrolling Interest	Noncontrolling Interest As of June 30, 2018 , we have 5 VIEs included in our consolidated financial statements, all of which are NxStage Kidney Care dialysis centers. We are the managing member or we have a majority seat on the entity’s board of managers, manage these entities through a management services agreement. The analysis upon which these consolidation determinations rest are complex, involve uncertainties, and require significant judgment on various matters. At June 30, 2018 and December 31, 2017 , total assets of our VIEs were $7.3 million and $5.6 million , and total liabilities and noncontrolling interests of our VIEs were $8.2 million and $5.8 million , respectively. We have potential obligations to purchase the noncontrolling interests held by third parties in certain of our consolidated subsidiaries. These obligations are in the form of put provisions and are contingently exercisable at the third-party owners' discretion given specific facts and circumstances as outlined in each specific put provision. If these put provisions were exercised, we would be required to purchase all the third-party owners' noncontrolling interests at a fair value at the time of exercise pursuant to the terms of the agreement. At June 30, 2018 the Company's noncontrolling interests subject to put provisions were $(0.2) million and none of the rights were exercisable. The following table sets forth the changes in noncontrolling interest not subject to put provisions for the three and six months ended June 30, 2018 and 2017 (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Balance at beginning of period $ 273 $ 297 $ (12 ) $ 625 Adjustment due to adoption of ASC 606 (25 ) — 542 — Net loss attributable to noncontrolling interest in consolidated subsidiary 393 (442 ) 111 (770 ) Balance at end of period $ 641 $ (145 ) $ 641 $ (145 )

Derivative Instruments and Hedg

Derivative Instruments and Hedging	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging	Derivative Instruments and Hedging We operate manufacturing and service facilities in Mexico, Germany, and Italy, and we purchase materials and pay our employees at those facilities in pesos and euros, and as such, we are potentially exposed to adverse as well as beneficial movements in currency exchange rates. We enter into foreign exchange forward contracts to minimize the impact of currency exchange rate fluctuations on these peso and euro denominated expenses. These contracts have durations of up to twelve months and are designated as cash flow hedges. The counterparties to these foreign exchange forward contracts are creditworthy financial institutions; therefore, we do not consider the risk of counterparty nonperformance to be material. As of June 30, 2018 and December 31, 2017 , the notional amount of our outstanding contracts that are designated as cash flow hedges was $25.5 million and $24.1 million , respectively. The fair value of these contracts is recorded on the balance sheet within prepaid expenses and other current assets or accrued expenses depending on the gain (loss) position. The fair value of these contracts was a net liability of $0.3 million at June 30, 2018 and a net asset of less than $0.1 million at December 31, 2017 , respectively. The cash flows related to our currency exchange contracts are classified as operating cash flows, which is consistent with the cash flow treatment of the underlying items being hedged. Gains or losses related to hedge ineffectiveness recognized in earnings were not material during the six months ended June 30, 2018 and 2017 . Given the short-term nature of our contracts, any gains or losses recorded within accumulated other comprehensive income (loss) will be recognized in earnings within the next twelve months. The following table presents the effect of these contracts designated as cash flow hedges on our condensed consolidated financial statements (in thousands): Gain (Loss) Recognized in OCI (Effective Portion) Gain (Loss) Reclassified from OCI into Income (Effective Portion) Classification within the Condensed Consolidated Statement of Comprehensive Loss Three Months Ended June 30, 2018 Foreign exchange forward contracts $ (535 ) $ 421 Cost of revenues Six Months Ended June 30, 2018 Foreign exchange forward contracts $ 819 $ 975 Cost of revenues Three Months Ended June 30, 2017 Foreign exchange forward contracts $ 1,563 $ 121 Cost of revenues Six Months Ended June 30, 2017 Foreign exchange forward contracts $ 4,095 $ (480 ) Cost of revenues

Accumulated Other Comprehensive

Accumulated Other Comprehensive (Loss) Income	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Accumulated Other Comprehensive (Loss) Income	Accumulated Other Comprehensive (Loss) Income The following additional information is provided with respect to the accumulated other comprehensive (loss) income as presented on the condensed consolidated balance sheets (in thousands): Unrealized gain (loss) on derivative instruments Other (2) Total Balance, net of tax, as of December 31, 2017 $ (1,284 ) $ (2,389 ) $ (3,673 ) Other comprehensive income (loss) before reclassifications, net of $206 tax during 2018 614 (544 ) 70 Gain reclassified to earnings (1) (975 ) — (975 ) Total other comprehensive loss, net of tax (361 ) (544 ) (905 ) Balance, net of tax, as of June 30, 2018 $ (1,645 ) $ (2,933 ) $ (4,578 ) (1) Reclassifications of gains (losses) on derivative instruments are included in cost of revenues on the condensed consolidated statement of comprehensive loss. See Note 15 , Derivative Instruments and Hedging for further information. (2) Other includes cumulative translation adjustments and, to a lesser extent, pension benefits.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We have certain financial assets and liabilities measured at fair value on a recurring and non-recurring basis recorded in our condensed consolidated balance sheets. The fair value measurements used are based on quoted prices, when available, or through the use of alternative approaches. The inputs used to determine fair value have been classified as Level 1, 2 or 3. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Fair values determined by Level 2 inputs utilize data points that are observable such as quoted prices, interest rates and yield curves for similar instruments and model-derived valuations whose inputs are observable. Fair values determined by Level 3 inputs utilize unobservable data points for the asset or liability. We measure the fair value of our foreign exchange forward contracts classified as derivative instruments using an income approach, based on prevailing market forward rates less the contract rate multiplied by the notional amount. The product of this calculation is then adjusted for counterparty risk. We did not have any transfers between Level 1 and Level 2 and Level 3 during the six months ended June 30, 2018 . The following tables present assets and liabilities measured at fair value on a recurring basis and their level within the value hierarchy (in thousands): June 30, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value Assets Money market funds (1) $ 35,248 $ — $ — $ 35,248 Foreign exchange forward contracts (2) — 261 — 261 Liabilities Foreign exchange forward contracts (2) $ — $ 545 $ — $ 545 December 31, 2017 Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Total Fair Value Assets Money market funds (1) $ 35,020 $ — $ — $ 35,020 Foreign exchange forward contracts (2) — 690 — 690 Liabilities Foreign exchange forward contracts (2) $ — $ 661 $ — $ 661 (1) Money market funds are included within cash and cash equivalents. (2) Foreign exchange forward contracts are included within prepaid expenses and other current assets or accrued expenses depending on the gain (loss) position. The carrying amount of our long-term debt approximates fair value at June 30, 2018 and December 31, 2017 . The fair value of our long-term debt was estimated using inputs derived principally from market observable data, including current rates offered to us for debt of the same or similar remaining maturities. Within the hierarchy of fair value measurements, these are Level 2 inputs. The carrying amounts reflected in the condensed consolidated balance sheets for cash and cash equivalents (including money market funds), accounts receivable, prepaid expenses and other current and non-current assets, accounts payable and accrued expenses approximate fair value due to their short-term nature. At June 30, 2018 and December 31, 2017 , we had an equity instrument without readily determinable fair values of $2.5 million for which we have elected the measurement alternative. We have evaluated this investment for any impairment, as well as any observable price changes for an identical or similar equity instrument of the same issuer, and determined that no material adjustment in the carrying value was required for the six months ended June 30, 2018 .

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	6 Months Ended
	Jun. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information The following additional information is provided with respect to the condensed consolidated statements of cash flows (in thousands): Six Months Ended June 30, 2018 2017 Noncash Investing and Financing Activities: Transfers from inventory to field equipment $ 10,912 $ 10,254 Transfers from field equipment to deferred cost of revenues 7,770 4,983 Market value of shares received in payment for exercise of stock options 887 2,524 PP&E financed by construction liability 95 109

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements as of June 30, 2018 and December 31, 2017 and for the three and six months ended June 30, 2018 and 2017 , and related notes, are unaudited but, in the opinion of our management, include all adjustments, consisting of normal recurring adjustments, that are necessary for fair statement of the interim periods presented. Our unaudited condensed consolidated financial statements have been prepared following the requirements of the Securities and Exchange Commission (SEC) for interim reporting. As permitted under these rules, we have condensed or omitted certain footnotes and other financial information that are normally required by U.S. generally accepted accounting principles (GAAP). Our accounting policies are described in the notes to the consolidated financial statements in our Annual Report on Form 10-K for the year ended December 31, 2017 ( 2017 Annual Report) and updated, as necessary, in this Quarterly Report on Form 10-Q (Quarterly Report). Operating results for any interim period are not necessarily indicative of results for the entire year or future periods. The December 31, 2017 condensed consolidated balance sheet contained herein was derived from audited financial statements, but does not include all disclosures that would be required for audited financial statements under GAAP. For further information, refer to the consolidated financial statements and footnotes thereto included in our 2017 Annual Report.
Use of Estimates	The preparation of our condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure 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 could differ from those estimates. Such financial statements reflect all adjustments that, in the opinion of management, are necessary for a fair presentation of the results of the periods presented. All such adjustments are of a normal recurring nature.
Principles of Consolidation	Principles of Consolidation Our condensed consolidated financial statements include the accounts of NxStage Medical, Inc. and our wholly-owned subsidiaries and other entities in which we maintain a majority voting interests or for which we maintain effective control, including variable interest entities ("VIEs") for which we are deemed the primary beneficiary. All significant intercompany balances and transactions have been eliminated. Noncontrolling interests represent the proportionate equity interests in the consolidated entities that are not wholly owned by us. Noncontrolling interests of acquired entities are recognized at their initial fair value.
Revenue Recognition	Revenue Recognition We recognize revenue from product sales and services when earned through fulfillment of our performance obligations. The amount of revenue recognized is based on the total consideration that we ultimately expect to collect relative to the good or service provided. We estimate the standalone selling price for an individual performance obligation based on consideration of both industry and Company-specific factors, including the profit margin for similar products, the cost to produce the deliverable and the anticipated margin on that deliverable and the characteristics of the varying markets in which the deliverable is sold. Any tax assessed by a governmental authority that is incurred as a result of a revenue transaction (e.g. sales tax) is excluded from revenues and reported on a net basis. In general, we do not have any significant extended payment terms as payment is received at or shortly after the point of sale. The expected costs associated with our standard product warranties continue to be recognized as expense when the products are sold. When shipping and handling activities are performed after the transfer of control to the customer (e.g., when control transfers prior to delivery), they are considered as fulfillment activities, and accordingly, the costs are accrued for when the related revenue is recognized. System One Segment We derive revenue in the home market primarily from sales of the System One hardware and sales of disposable products. We enter into arrangements with customers that may include multiple elements including equipment lease transactions pursuant to the depot service model described below or equipment sales with no post-delivery obligations other than standard warranty obligations, disposable product sales and services. The transaction price is allocated to the elements including allocation to the lease and non-lease elements of the arrangement, where applicable, based on their relative standalone selling price and recognized pursuant to the applicable guidance. System One hardware sales to dialysis clinic customers in the home market are made under the depot service model whereby equipment requiring service is picked up and a replacement device is shipped to the site of care. Accordingly, we recognize upfront fees received from equipment transactions as revenue on a straight-line basis over the term of our remaining service obligation, which generally range between 5 and 7 years, and direct costs relating to the delivered equipment are classified in deferred cost of revenues and amortized over the same expected period as the related revenue. Disposable products sales are recognized in accordance with the contract terms. We also offer a month-to-month System One hardware rental arrangements. Under these arrangements, revenue is recognized on a monthly basis in accordance with agreed upon arrangements with the customers. Our sales arrangements with our international distributors are structured as direct product sales and have no significant post-delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. In the critical care market, we structure sales of the System One and disposable products as direct product sales and have no significant post-delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Certain of these arrangements provide for training, technical support and equipment service to our customers. We recognize training and technical support revenue when the related services are performed and our performance obligations are satisfied. In the case of equipment service contracts entered into after the initial standard warranty period, the service contract revenue is recognized ratably over the service period. Some of our contracts with customers in the System One segment contain contractually determined volume discounts offered to similar classes of customers. In addition, in many agreements we offer rebates and discounts for early payment which result in the ultimate payment being variable. The variable consideration paid by the customer is estimated and recognized when we satisfy our performance obligation (generally upon delivery) to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized to date will not occur. We are able to reliably estimate the amount of rebates and discounts and record them as a reduction to revenue and accounts receivable at the time of sale. In-Center Segment Our In-Center segment sales are structured as direct product sales primarily through distributors, and we have no significant post-delivery obligations with the exception of standard warranty obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Some of our distribution contracts for the In-Center segment contain rebates and discounts for early payment which results in the ultimate payment being variable. The variable fee paid by the distributor is estimated and recognized when we satisfy our performance obligation (generally upon delivery to the distributor) to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized to date will not occur. We are able to reliably estimate the amount of rebates/discounts and record them as a reduction to revenue and trade accounts receivable at the time of sale. Services Segment Revenues in our Services segment are derived from dialysis care services provided to patients at our NxStage Kidney Care dialysis centers. Revenues are recognized in the period in which services are provided. For revenues associated with Medicare, Medicaid or commercial insurers with which we have formal agreements, revenue is recognized based on contractual rates or rates established by statute or regulation in the case of Medicare and Medicaid. For certain classes of payors, for example non-contracted commercial health insurance payors and amounts due from patients (including co-pay and deductible amounts), revenue is recognized based on our estimate of the consideration that will be ultimately received from the payor which results in the ultimate payment being variable. The variable fee is estimated using historical collections experience with similar classes of payors and recognized when we satisfy our performance obligation (when services are provided) to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized to date will not occur. Overall, these estimates reflect the Company’s best estimates of the amount of consideration to which it is entitled from these customers. The amount of variable consideration which is included in the transaction price may be constrained, and is included in the sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from our estimates. If actual results in the future vary from our estimates, we adjust these estimates, which would affect revenues and earnings in the period such variances become known. Such changes, if material, will be disclosed in the period such variances become known. Other Other revenues relate to the manufacturing of dialyzers for sale to Asahi Kasei Kuraray Medical Co. (Asahi). Sales to Asahi are structured as direct product sales and we have no significant post-delivery obligations. Revenue from direct product sales is recognized upon delivery in accordance with contract terms. Costs to Obtain or Fulfill a Contract We capitalize commission fees as costs of obtaining a contract, when they are incremental and if they are expected to be recovered, and amortize them consistently with the pattern of transfer of the good to which the asset relates. If the expected amortization period is one year or less, the commission fee is expensed when incurred. Direct costs related to the delivered equipment within the System One home market are capitalized as deferred cost of revenues and amortized over the same expected period as the related revenue.
Concentration of Credit Risk	Concentration of Credit Risk Concentration of credit risk with respect to accounts receivable is primarily limited to certain customers to whom we make substantial sales.
Warranty Costs	Warranty Costs We accrue estimated costs that we may incur under our product warranty programs at the time the product revenue is recognized, based on contractual rights and historical experience. Warranty expense is included in cost of revenues in the condensed consolidated statements of comprehensive loss.
Intangibles and Other Long-Lived Assets	Intangibles and Other Long-Lived Assets Intangible assets are carried at cost less accumulated amortization. For assets with determinable useful lives, amortization is recognized using the straight-line method over the estimated economic lives of the respective intangible assets. Long-lived assets, including intangible assets, are evaluated for recoverability whenever events or circumstances indicate that their carrying value may not be recoverable. Recoverability of long-lived assets is assessed at the lowest level for which discrete cash flows are available and is measured by comparing the asset group’s carrying value to its expected non-discounted future cash flows. If the sum of the expected non-discounted future cash flows is less than the carrying amount of the long-lived assets, an impairment loss is recognized for excess of the carrying amount of the asset group over its fair value. In the second quarter of 2018 , events and circumstances have indicated that certain long-lived tangible assets in the Services segment may not be recoverable. Therefore, a recoverability test was performed at the center level by comparing the carrying value of each center to its estimated future undiscounted cash flows, within the initial lease term (which is the equivalent to the depreciable life of the centers' most significant asset, its leasehold improvements). As of June 30, 2018 , our expected non-discounted future cash flows for the majority of our centers indicated such carrying amounts were expected to be recovered. We recorded an impairment charge during the second quarter of 2018 of $0.1 million in cost of revenue to write-down certain center level assets within our Services segment. Our expected non-discounted future cash flows used in our impairment testing are based upon cash flow projections and, if appropriate, include assumed proceeds upon sale of the asset group at the end of the cash flow period. We believe our procedures for developing cash flow projections, including the estimated sales proceeds, are reasonable and consistent with current market conditions for each of the dates when impairment testing has been performed. Developing cash flow projections requires significant estimates and judgment. Among other things, slower than expected patient ramp or lower than expected reimbursement rates would negatively impact our cash flow projections in the near term. Fair value of the asset group was estimated using a discounted cash flow approach. Estimating fair value requires significant judgment in the selection of the valuation technique and assumptions used in developing cash flow projections, growth rates and discount rates. Our assumptions are based on our best estimates, using appropriate and customary market participant assumptions. Any adverse changes in certain valuation assumptions could result in the need to record additional impairment to write down all or a portion the centers’ remaining asset carrying value. We had $11.5 million of long-lived assets at our Services segment at June 30, 2018 . It is reasonably possible that our cash flow projections may change in the near term resulting in the need to record an impairment charge for at least some portion of these assets.
Goodwill	Goodwill We test goodwill for impairment during the fourth quarter, or more frequently when events or changes in circumstances indicate that the goodwill might be impaired. This test includes first a qualitative assessment and then, if necessary, a quantitative assessment to determine if the fair value of a reporting unit is less than its carrying amount. Our System One, In-center and Services reporting units contain goodwill of $41.1 million , $0.5 million and $1.1 million , respectively. Factors considered in the qualitative assessment include, but are not limited to, both macroeconomic conditions and entity-specific conditions. For the quantitative assessment the reporting unit's fair value is estimated using a discounted cash flow or other fair value measurement. During 2017 and 2016 we utilized the qualitative assessment to assess the fair value of our System One and In-center reporting units and concluded that it was more likely than not that the fair value of our reporting units was greater than their carrying value. During 2017 , we also utilized the qualitative assessment to assess the fair value of our Services reporting unit and concluded that it was more likely than not that the fair value of the reporting unit was greater than its carrying value. During 2016, for our Services reporting unit, we utilized the quantitative assessment noting that the fair value of the reporting unit exceeds its carrying value, indicating that goodwill was not impaired. We estimated the fair value of our Services reporting unit using a discounted cash flow approach. Estimating the fair value of our Services reporting unit requires significant judgment in the selection of the valuation technique and assumptions used in cash flow projections, growth rates and discount rates. Our assumptions are based on our best estimates, using appropriate and customary market participant assumptions. There have been no events or changes in circumstances since the date of our last goodwill impairment tests that would indicate it is more likely than not that the fair value of our reporting units is less than their carrying value. Developing cash flow projections involves significant judgment with respect to patient additions and reimbursement rates, operating income, capital expenditures and changes in working capital. Reductions in our cash flow projections due to slower than expected patient ramp or lower than expected reimbursement rates, among other things, or adverse changes in certain valuation assumptions or changes in the reporting units net assets could result in a goodwill impairment charge of up to $1.1 million in our Services reporting unit in the future.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Implemented Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued ASU No. 2014-9: “Revenue from Contracts with Customers” (ASC 606). The standard provides that revenue should be recognized when an entity transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In addition, the standard requires disclosure of the nature, amount, timing and uncertainty of revenues and cash flow arising from contracts with customers. The FASB has issued several amendments and updates to the new revenue standard, including how an entity should identify performance obligations. As amended, the new guidance was effective for us beginning January 1, 2018. We adopted ASC 606 using the modified retrospective method approach as of January 1, 2018. This approach was applied to all contracts not completed as of January 1, 2018. We recognized the cumulative effect of initially applying the new revenue standard as an adjustment to the opening balance of retained earnings. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. See above in Note 2 for discussion of our updated Revenue Recognition policy. We do not expect the adoption of the new revenue standard to have a material impact to our net income on an ongoing basis. The adoption of ASC 606 impacted the timing of revenue recognition for our Services segment and resulted in enhanced footnote disclosures related to customer contracts as included in Note 3 to these condensed consolidated financial statements. It also modified the accounting for commissions fees as it requires such incremental and recoverable costs to be capitalized and amortized over the estimated life of the asset. Previously, these costs were expensed as incurred. The cumulative effect of the changes made to our condensed consolidated balance sheet for the adoption of ASC 606 was as follows (in thousands): As Reported Adjustment due to ASC 606 December 31, 2017 January 1, 2018 ASSETS Accounts receivable, net $ 31,625 $ 4,419 $ 36,044 Prepaid expenses and other current assets 7,609 1,895 9,504 Deferred cost of revenues 31,410 (139 ) 31,271 Other assets 5,911 379 6,290 LIABILITIES AND STOCKHOLDERS’ EQUITY Noncontrolling interests subject to put provisions (165 ) 49 (116 ) Accumulated deficit (421,593 ) 5,961 (415,632 ) Noncontrolling interests not subject to put provisions (12 ) 544 532 In accordance with the new revenue standard requirements, the disclosure of the impact of adoption on our condensed consolidated statement of comprehensive loss for the three and six months ended June 30, 2018 was as follows (in thousands): Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 As Reported Balance without adoption of ASC 606 Effect of Change As Reported Adjustment to ASC 606 Effect of Change Revenues $ 106,970 $ 107,293 $ (323 ) $ 214,268 $ 215,727 $ (1,459 ) Cost of revenues 61,023 61,068 (45 ) 122,156 122,262 (106 ) Selling and marketing 18,131 18,196 (65 ) 36,186 36,351 (165 ) In accordance with the new revenue standard requirements, the disclosure of the impact of adoption on our condensed consolidated balance sheet at June 30, 2018 was as follows (in thousands): June 30, 2018 ASSETS As Reported Balance without adoption of ASC 606 Effect of Change Accounts receivable, net $ 34,506 $ 31,269 $ 3,237 Prepaid expenses and other current assets 8,310 6,269 2,041 Deferred cost of revenues 32,493 32,525 (32 ) Other assets 6,203 5,805 398 LIABILITIES AND STOCKHOLDERS’ EQUITY Noncontrolling interests subject to put provisions $ (197 ) $ (227 ) $ 30 Accumulated deficit (419,680 ) (425,268 ) 5,588 Noncontrolling interests not subject to put provisions 641 619 22 Accumulated other comprehensive loss (4,578 ) (4,582 ) 4 The impacts noted above are primarily attributable to the change in the timing of revenue recognition for our Services segment as the standard requires revenues to be estimated and recognized upon transfer of the promised goods and services and accounting for capitalization of certain commissions. In January 2016, the FASB issued ASU No. 2016-01: “Financial Instruments-Overall: Recognition and Measurement of Financial Assets and Financial Liabilities” which impacts the recognition, measurement, presentation and disclosure of financial assets and financial liabilities. Among other things, the standard generally requires all equity investments (except those accounted for under the equity method and those that result in consolidation of the investee) be measured at fair value through earnings. For those equity instruments that do not have readily determinable fair values, the standard permits the application of a measurement alternative using the cost of the investment, less any impairments, plus or minus changes resulting from observable price changes for an identical or similar investment of the same issuer with such changes recognized in net income. The new guidance was effective for us beginning January 1, 2018. We have made this measurement alternative policy election for our equity investments without readily determinable fair values. The adoption of this standard did not have an impact on our financial position or results of operation. Recent Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02: "Accounting for Leases" which amends the existing accounting standards for leases. The new standard requires lessees to record a right-of-use asset and a corresponding lease liability on the balance sheet for all leases with terms longer than twelve months. For lessees, leases will continue to be classified as either operating or financing in the income statement. This ASU is required to be applied with a modified retrospective approach which gives the option of applying the new lease requirements as of the effective date with enhanced disclosure requirements for comparative periods presented under the current guidance or applying the new standard at the beginning of the earliest comparative period presented. The new guidance is effective for us beginning January 1, 2019 and early adoption is permitted. We are evaluating the method of adoption and the potential impact of the standard on our consolidated financial statements and related disclosures and are comparing our current policies and practices to the requirements of the standard. We have developed a project plan to develop processes and tools in order to adopt the standard on January 1, 2019. We have periodically briefed our Audit Committee on our progress made towards adoption. In August 2017, the FASB issued ASU 2017-12: "Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities" which amends the hedge accounting recognition and presentation requirements. The update is intended to more closely align hedge accounting with companies’ risk management strategies, simplify the application of hedge accounting and increase transparency as to the scope and results of hedge programs. The update is effective for us beginning January 1, 2019, with early adoption permitted. We are currently evaluating the potential impact this update will have on our financial statements.
Net Loss per Share	Net Loss per Share Basic net loss per share is computed by dividing loss attributable to NxStage Medical, Inc. common stockholders (the numerator) by the weighted-average number of common shares outstanding (the denominator) for the period. The computation of diluted loss per share is similar to basic loss per share, except that the denominator is increased to include the number of additional common shares that would have been outstanding if the potentially dilutive common shares had been issued.
Segment Disclosure	We have three reportable business segments: System One, In-Center, and Services. The operating results of NxStage Kidney Care are included in our Services segment. We refer to our System One segment, In-Center segment, and Other category as our products business. Our System One segment includes revenues from sales and rentals of the System One and PureFlow SL dialysate preparation equipment and the sale of disposable products to customers in the home market, including through our NxStage Kidney Care dialysis centers, and critical care market. The home market is devoted to the treatment of ESRD patients in the home or a home-like setting, including skilled nursing facilities, while the critical care market is devoted to the treatment of hospital-based patients with acute kidney failure or fluid overload. Some of our largest customers in the home market provide outsourced renal dialysis services to some of our customers in the critical care market. Sales of product to both markets are made primarily through dedicated sales forces and distributed directly to the customer, or the patient, with certain products sold through distributors. Our In-Center segment includes revenues from the sale of blood tubing sets and needles for hemodialysis primarily for the treatment of ESRD patients at dialysis centers and needles for apheresis. Nearly all In-Center products are sold through national distributors. The remainder of our products business, which is included within the Other category, relates to the manufacturing of dialyzers for sale to Asahi Kasei Kuraray Medical Co., Ltd. (Asahi) and research and development and general and administrative expenses that are excluded from the segment operating performance measures. Our Services segment includes revenues from dialysis services provided to patients at our NxStage Kidney Care dialysis centers. Sales of the System One and related products to our NxStage Kidney Care dialysis centers are included in System One segment revenues, which are then eliminated upon consolidation. The accounting policies of our reportable segments are described in Note 2 to the consolidated financial statements included in our 2017 Annual Report and updated, as necessary, in Note 2 to the condensed consolidated financial statements included in this Quarterly Report. Our chief operating decision maker allocates resources to our business segments and assesses segment performance based on segment profit (loss), which consists of revenues less cost of revenues, selling and marketing and distribution expenses.
Fair Value Measurements	Fair Value Measurements We have certain financial assets and liabilities measured at fair value on a recurring and non-recurring basis recorded in our condensed consolidated balance sheets. The fair value measurements used are based on quoted prices, when available, or through the use of alternative approaches. The inputs used to determine fair value have been classified as Level 1, 2 or 3. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Fair values determined by Level 2 inputs utilize data points that are observable such as quoted prices, interest rates and yield curves for similar instruments and model-derived valuations whose inputs are observable. Fair values determined by Level 3 inputs utilize unobservable data points for the asset or liability. We measure the fair value of our foreign exchange forward contracts classified as derivative instruments using an income approach, based on prevailing market forward rates less the contract rate multiplied by the notional amount. The product of this calculation is then adjusted for counterparty risk.

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Schedule of Rollforward of Warranty Accrual	The following is a rollforward of our warranty accrual (in thousands): Balance at December 31, 2017 $ 293 Provision 173 Usage (224 ) Balance at June 30, 2018 $ 242
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The cumulative effect of the changes made to our condensed consolidated balance sheet for the adoption of ASC 606 was as follows (in thousands): As Reported Adjustment due to ASC 606 December 31, 2017 January 1, 2018 ASSETS Accounts receivable, net $ 31,625 $ 4,419 $ 36,044 Prepaid expenses and other current assets 7,609 1,895 9,504 Deferred cost of revenues 31,410 (139 ) 31,271 Other assets 5,911 379 6,290 LIABILITIES AND STOCKHOLDERS’ EQUITY Noncontrolling interests subject to put provisions (165 ) 49 (116 ) Accumulated deficit (421,593 ) 5,961 (415,632 ) Noncontrolling interests not subject to put provisions (12 ) 544 532 In accordance with the new revenue standard requirements, the disclosure of the impact of adoption on our condensed consolidated statement of comprehensive loss for the three and six months ended June 30, 2018 was as follows (in thousands): Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 As Reported Balance without adoption of ASC 606 Effect of Change As Reported Adjustment to ASC 606 Effect of Change Revenues $ 106,970 $ 107,293 $ (323 ) $ 214,268 $ 215,727 $ (1,459 ) Cost of revenues 61,023 61,068 (45 ) 122,156 122,262 (106 ) Selling and marketing 18,131 18,196 (65 ) 36,186 36,351 (165 ) In accordance with the new revenue standard requirements, the disclosure of the impact of adoption on our condensed consolidated balance sheet at June 30, 2018 was as follows (in thousands): June 30, 2018 ASSETS As Reported Balance without adoption of ASC 606 Effect of Change Accounts receivable, net $ 34,506 $ 31,269 $ 3,237 Prepaid expenses and other current assets 8,310 6,269 2,041 Deferred cost of revenues 32,493 32,525 (32 ) Other assets 6,203 5,805 398 LIABILITIES AND STOCKHOLDERS’ EQUITY Noncontrolling interests subject to put provisions $ (197 ) $ (227 ) $ 30 Accumulated deficit (419,680 ) (425,268 ) 5,588 Noncontrolling interests not subject to put provisions 641 619 22 Accumulated other comprehensive loss (4,578 ) (4,582 ) 4

Revenues (Tables)

Revenues (Tables)	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table disaggregates our revenues by market (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2018 System One segment Home $ 61,755 120,434 Critical Care 22,325 46,533 Total System One segment 84,080 166,967 In-Center segment 16,389 33,746 Other 2,522 5,342 Products subtotal 102,991 206,055 Services segment 5,184 10,603 Elimination of intersegment revenues (1,205 ) (2,390 ) Total $ 106,970 $ 214,268

Inventory (Tables)

Inventory (Tables)	6 Months Ended
	Jun. 30, 2018
Inventory Disclosure [Abstract]
Components of Inventory	The components of inventory are as follows (in thousands): June 30, December 31, Purchased components $ 14,373 $ 14,947 Work in process 15,275 13,433 Finished goods 20,670 20,832 Total $ 50,318 $ 49,212

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Schedule of Anti-dilutive Net Loss Per Share	The following potential common stock equivalents, as calculated using the treasury stock method, were not included in the computation of diluted net loss per share as their effect would have been anti-dilutive due to the net loss incurred (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Options to purchase common stock 1,102 1,002 1,030 1,166 Unvested restricted stock 160 196 196 260 Total 1,262 1,198 1,226 1,426

Accrued Expenses, Other Curre29

Accrued Expenses, Other Current Liabilities and Other Long-Term Liabilities (Tables)	6 Months Ended
	Jun. 30, 2018
Payables and Accruals [Abstract]
Components of Accrued Expenses	The components of accrued expenses are as follows (in thousands): June 30, December 31, Payroll, compensation and related benefits $ 14,825 $ 13,195 Distribution expenses 5,419 4,914 Other 10,903 9,876 Total $ 31,147 $ 27,985
Components of Other Current liabilities	The components of other current liabilities are as follows (in thousands): June 30, December 31, Capital lease obligations $ 2,006 $ 2,131 Deferred revenue, current portion 1,309 1,473 Other 870 955 Total $ 4,185 $ 4,559
Components of Other Long-term Liabilities	The components of other long-term liabilities are as follows (in thousands): June 30, December 31, Capital lease obligations $ 10,908 $ 11,589 Lease incentive obligations 2,591 2,652 Benefit plan obligations 2,031 2,060 Other 1,634 1,523 Total $ 17,164 $ 17,824

Segment Disclosures (Tables)

Segment Disclosures (Tables)	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Summary of Operating Performance of Reportable Segments	The following summarizes the operating performance of our reportable segments (in thousands): System One In-Center Other Services Intersegment Elimination Total Three Months Ended June 30, 2018 Revenues from external customers $ 82,875 $ 16,389 $ 2,522 $ 5,184 $ — $ 106,970 Intersegment revenues 1,205 — — — (1,205 ) — Revenues 84,080 16,389 2,522 5,184 (1,205 ) 106,970 Segment profit (loss) 22,765 2,436 (20,458 ) (5,867 ) 35 (1,089 ) Depreciation and amortization 5,829 463 1,077 1,319 (46 ) 8,642 Three Months Ended June 30, 2017 Revenues from external customers $ 74,197 14,326 2,836 4,857 $ — $ 96,216 Intersegment revenues 1,261 — — — (1,261 ) $ — Revenues 75,458 14,326 2,836 4,857 (1,261 ) 96,216 Segment profit (loss) 21,374 1,662 (18,582 ) (6,493 ) (17 ) (2,056 ) Depreciation and amortization 5,428 544 1,092 1,302 5 8,371 Six Months Ended June 30, 2018 Revenues from external customers $ 164,577 $ 33,746 $ 5,342 $ 10,603 $ — $ 214,268 Intersegment revenues 2,390 — — — (2,390 ) — Revenues 166,967 33,746 5,342 10,603 (2,390 ) 214,268 Segment profit (loss) 44,485 4,735 (40,083 ) (11,426 ) 70 (2,219 ) Depreciation and amortization 11,264 951 2,161 2,662 (92 ) 16,946 Six Months Ended June 30, 2017 Revenues from external customers $ 147,471 29,932 5,735 9,907 $ — $ 193,045 Intersegment revenues 2,648 — — — (2,648 ) — Revenues 150,119 29,932 5,735 9,907 (2,648 ) 193,045 Segment profit (loss) 41,222 4,021 (36,843 ) (12,098 ) (39 ) (3,737 ) Depreciation and amortization 11,062 1,069 2,164 2,570 (27 ) 16,838
Summary of Customers Who Individually Make Up Greater than 10% of Total Revenues	The following table summarizes the number of customers who individually make up greater than ten percent of total revenues: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 DaVita 19 % 20 % 19 % 20 % Fresenius 21 % 20 % 20 % 19 %

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock-Based Compensation Expense in Consolidated Statements of Comprehensive Loss	The following table presents stock-based compensation expense included in our condensed consolidated statements of comprehensive loss (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Cost of revenues $ 220 $ 263 $ 471 $ 567 Selling and marketing 749 1,137 1,576 1,993 Research and development 311 334 693 717 General and administrative 1,000 1,016 2,237 2,047 Total $ 2,280 $ 2,750 $ 4,977 $ 5,324

Noncontrolling Interest (Tables

Noncontrolling Interest (Tables)	6 Months Ended
	Jun. 30, 2018
Noncontrolling Interest [Abstract]
Schedule of Changes in Noncontrolling Interest	The following table sets forth the changes in noncontrolling interest not subject to put provisions for the three and six months ended June 30, 2018 and 2017 (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Balance at beginning of period $ 273 $ 297 $ (12 ) $ 625 Adjustment due to adoption of ASC 606 (25 ) — 542 — Net loss attributable to noncontrolling interest in consolidated subsidiary 393 (442 ) 111 (770 ) Balance at end of period $ 641 $ (145 ) $ 641 $ (145 )

Derivative Instruments and He33

Derivative Instruments and Hedging (Tables)	6 Months Ended
	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Effect of Contracts Designated as Cash Flow Hedges on Consolidated Financial Statements	The following table presents the effect of these contracts designated as cash flow hedges on our condensed consolidated financial statements (in thousands): Gain (Loss) Recognized in OCI (Effective Portion) Gain (Loss) Reclassified from OCI into Income (Effective Portion) Classification within the Condensed Consolidated Statement of Comprehensive Loss Three Months Ended June 30, 2018 Foreign exchange forward contracts $ (535 ) $ 421 Cost of revenues Six Months Ended June 30, 2018 Foreign exchange forward contracts $ 819 $ 975 Cost of revenues Three Months Ended June 30, 2017 Foreign exchange forward contracts $ 1,563 $ 121 Cost of revenues Six Months Ended June 30, 2017 Foreign exchange forward contracts $ 4,095 $ (480 ) Cost of revenues

Accumulated Other Comprehensi34

Accumulated Other Comprehensive (Loss) Income (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Summary of Additional Information on Accumulated Other Comprehensive (Loss) Income	The following additional information is provided with respect to the accumulated other comprehensive (loss) income as presented on the condensed consolidated balance sheets (in thousands): Unrealized gain (loss) on derivative instruments Other (2) Total Balance, net of tax, as of December 31, 2017 $ (1,284 ) $ (2,389 ) $ (3,673 ) Other comprehensive income (loss) before reclassifications, net of $206 tax during 2018 614 (544 ) 70 Gain reclassified to earnings (1) (975 ) — (975 ) Total other comprehensive loss, net of tax (361 ) (544 ) (905 ) Balance, net of tax, as of June 30, 2018 $ (1,645 ) $ (2,933 ) $ (4,578 ) (1) Reclassifications of gains (losses) on derivative instruments are included in cost of revenues on the condensed consolidated statement of comprehensive loss. See Note 15 , Derivative Instruments and Hedging for further information. (2) Other includes cumulative translation adjustments and, to a lesser extent, pension benefits.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables present assets and liabilities measured at fair value on a recurring basis and their level within the value hierarchy (in thousands): June 30, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value Assets Money market funds (1) $ 35,248 $ — $ — $ 35,248 Foreign exchange forward contracts (2) — 261 — 261 Liabilities Foreign exchange forward contracts (2) $ — $ 545 $ — $ 545 December 31, 2017 Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Total Fair Value Assets Money market funds (1) $ 35,020 $ — $ — $ 35,020 Foreign exchange forward contracts (2) — 690 — 690 Liabilities Foreign exchange forward contracts (2) $ — $ 661 $ — $ 661 (1) Money market funds are included within cash and cash equivalents. (2) Foreign exchange forward contracts are included within prepaid expenses and other current assets or accrued expenses depending on the gain (loss) position.

Supplemental Cash Flow Inform36

Supplemental Cash Flow Information (Tables)	6 Months Ended
	Jun. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Summary of Supplemental Cash Flow Information	The following additional information is provided with respect to the condensed consolidated statements of cash flows (in thousands): Six Months Ended June 30, 2018 2017 Noncash Investing and Financing Activities: Transfers from inventory to field equipment $ 10,912 $ 10,254 Transfers from field equipment to deferred cost of revenues 7,770 4,983 Market value of shares received in payment for exercise of stock options 887 2,524 PP&E financed by construction liability 95 109

Nature of Operations, Propose37

Nature of Operations, Proposed Merger, Basis of Presentation and Principles of Consolidation (Details) $ / shares in Units, $ in Millions	Jul. 10, 2018	Oct. 27, 2017USD ($)	Oct. 18, 2017	Jun. 30, 2018country	Aug. 07, 2017$ / shares
Accounting Policies [Abstract]
Number of countries in which entity operates | country				21
Fresenius Medical Care Holdings, Inc.
Business Acquisition [Line Items]
Share price (in dollars per share) | $ / shares					$ 30
Business combination, waiting period, extension term			30 days
Termination of merger agreement, extension term		90 days
Termination of merger agreement, fee paid to acquiree		$ 100
Termination of merger agreement, fee paid to acquirer		$ 60
Termination of merger agreement, period to publicly withdraw from the agreement before termination		10 days
Termination of merger agreement, period to not enter into alternative acquisition after termination		12 months
Subsequent Event | Fresenius Medical Care Holdings, Inc.
Business Acquisition [Line Items]
Termination of merger agreement, extension term	90 days

Summary of Significant Accoun38

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounting Policies [Line Items]
Goodwill	$ 42,748	$ 42,748	$ 42,748
System One
Accounting Policies [Line Items]
Goodwill	41,100	41,100
Services
Accounting Policies [Line Items]
Asset impairment recognized	100
Long-lived assets	11,500	11,500
Goodwill	1,100	1,100
In-Center
Accounting Policies [Line Items]
Goodwill	$ 500	$ 500
Minimum | System One
Accounting Policies [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period		5 years
Maximum | System One
Accounting Policies [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period		7 years

Summary of Significant Accoun39

Summary of Significant Accounting Policies - Schedule of Rollforward of Warranty Accrual (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]
Balance at beginning of period	$ 293
Provision	173
Usage	(224)
Balance at end of period	$ 242

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Cummulative Effect Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 34,506		$ 36,044	$ 31,625
Prepaid expenses and other current assets	8,310		9,504	7,609
Deferred cost of revenues	32,493		31,271	31,410
Other assets	6,203		6,290	5,911
Noncontrolling interests subject to put provisions	(197)		(116)	(165)
Accumulated deficit	(419,680)		(415,632)	(421,593)
Noncontrolling interests not subject to put provisions	641	$ 273	532	(12)	$ (145)	$ 297	$ 625
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	31,269			31,625
Prepaid expenses and other current assets	6,269			7,609
Deferred cost of revenues	32,525			31,410
Other assets	5,805
Noncontrolling interests subject to put provisions	(227)			(165)
Accumulated deficit	(425,268)			(421,593)
Noncontrolling interests not subject to put provisions	619			$ (12)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	3,237		4,419
Prepaid expenses and other current assets	2,041		1,895
Deferred cost of revenues	(32)		(139)
Other assets	398		379
Noncontrolling interests subject to put provisions	30		49
Accumulated deficit	5,588		5,961
Noncontrolling interests not subject to put provisions	$ 22		$ 544

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 106,970	$ 96,216	$ 214,268	$ 193,045
Cost of revenues	61,023	55,050	122,156	110,689
Selling and marketing	18,131	$ 16,841	36,186	$ 33,611
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	107,293		215,727
Cost of revenues	61,068		122,262
Selling and marketing	18,196		36,351
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(323)		(1,459)
Cost of revenues	(45)		(106)
Selling and marketing	$ (65)		$ (165)

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 34,506		$ 36,044	$ 31,625
Prepaid expenses and other current assets	8,310		9,504	7,609
Deferred cost of revenues	32,493		31,271	31,410
Other assets	6,203		6,290	5,911
Noncontrolling interests subject to put provisions	(197)		(116)	(165)
Accumulated deficit	(419,680)		(415,632)	(421,593)
Noncontrolling interests not subject to put provisions	641	$ 273	532	(12)	$ (145)	$ 297	$ 625
Accumulated other comprehensive loss	(4,578)			(3,673)
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	31,269			31,625
Prepaid expenses and other current assets	6,269			7,609
Deferred cost of revenues	32,525			31,410
Other assets	5,805
Noncontrolling interests subject to put provisions	(227)			(165)
Accumulated deficit	(425,268)			(421,593)
Noncontrolling interests not subject to put provisions	619			$ (12)
Accumulated other comprehensive loss	(4,582)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	3,237		4,419
Prepaid expenses and other current assets	2,041		1,895
Deferred cost of revenues	(32)		(139)
Other assets	398		379
Noncontrolling interests subject to put provisions	30		49
Accumulated deficit	5,588		5,961
Noncontrolling interests not subject to put provisions	22		$ 544
Accumulated other comprehensive loss	$ 4

Revenues (Details)

Revenues (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jan. 01, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 106,970,000	$ 214,268,000
Capitalized commission fees, period		21 months
Impairment losses, capitalized commissions		$ 0
System One
Disaggregation of Revenue [Line Items]
Revenues	84,080,000	166,967,000
System One | Home
Disaggregation of Revenue [Line Items]
Revenues	61,755,000	120,434,000
System One | Critical Care
Disaggregation of Revenue [Line Items]
Revenues	22,325,000	46,533,000
In-Center
Disaggregation of Revenue [Line Items]
Revenues	16,389,000	33,746,000
Other
Disaggregation of Revenue [Line Items]
Revenues	2,522,000	5,342,000
Other | Products
Disaggregation of Revenue [Line Items]
Revenues	102,991,000	206,055,000
Other | Services
Disaggregation of Revenue [Line Items]
Revenues	5,184,000	10,603,000
Intersegment Elimination
Disaggregation of Revenue [Line Items]
Revenues	(1,205,000)	(2,390,000)
Prepaid Expenses and Other Current Assets
Disaggregation of Revenue [Line Items]
Capitalized commission fees	$ 2,200,000	2,200,000	$ 2,000,000
Selling and marketing
Disaggregation of Revenue [Line Items]
Amortization expense, capitalized commissions		$ 1,200,000

Inventory - Components of Inven

Inventory - Components of Inventory (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Purchased components	$ 14,373	$ 14,947
Work in process	15,275	13,433
Finished goods	20,670	20,832
Total	$ 50,318	$ 49,212

Property and Equipment, Field E

Property and Equipment, Field Equipment and Deferred Cost of Revenues - Additional Information (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Deferred costs, accumulated amortization	$ 112.8	$ 106.3
Property And Equipment Excluding Field Equipment
Property, Plant and Equipment [Line Items]
Accumulated depreciation	62.4	56.8
Field Equipment
Property, Plant and Equipment [Line Items]
Accumulated depreciation	$ 53.3	$ 51.6

Intangible Assets - Additional

Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Accumulated amortization of intangible assets	$ 28	$ 27

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Anti-dilutive Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from computation of earnings per share (in shares)	1,262	1,198	1,226	1,426
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from computation of earnings per share (in shares)	1,102	1,002	1,030	1,166
Unvested restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential common stock equivalents excluded from computation of earnings per share (in shares)	160	196	196	260

Accrued Expenses, Other Curre48

Accrued Expenses, Other Current Liabilities and Other Long-Term Liabilities - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Payroll, compensation and related benefits	$ 14,825	$ 13,195
Distribution expenses	5,419	4,914
Other	10,903	9,876
Total	$ 31,147	$ 27,985

Accrued Expenses, Other Curre49

Accrued Expenses, Other Current Liabilities and Other Long-Term Liabilities - Components of Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Capital lease obligations	$ 2,006	$ 2,131
Deferred revenue, current portion	1,309	1,473
Other	870	955
Total	$ 4,185	$ 4,559

Accrued Expenses, Other Curre50

Accrued Expenses, Other Current Liabilities and Other Long-Term Liabilities - Components of Other Long-term Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Capital lease obligations	$ 10,908	$ 11,589
Lease incentive obligations	2,591	2,652
Benefit plan obligations	2,031	2,060
Other	1,634	1,523
Total	$ 17,164	$ 17,824

Segment Disclosures - Additiona

Segment Disclosures - Additional Information (Details)	6 Months Ended
	Jun. 30, 2018segment
Segment Reporting [Abstract]
Number of reporting segments	3

Segment Disclosures - Summary o

Segment Disclosures - Summary of Operating Performance of Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 106,970	$ 96,216	$ 214,268	$ 193,045
Segment profit (loss)	(1,089)	(2,056)	(2,219)	(3,737)
Depreciation and amortization	8,642	8,371	16,946	16,838
System One
Segment Reporting Information [Line Items]
Revenues	82,875	74,197	164,577	147,471
In-Center
Segment Reporting Information [Line Items]
Revenues	16,389	14,326	33,746	29,932
Services
Segment Reporting Information [Line Items]
Revenues	5,184	4,857	10,603	9,907
Operating Segments | System One
Segment Reporting Information [Line Items]
Revenues	84,080	75,458	166,967	150,119
Segment profit (loss)	22,765	21,374	44,485	41,222
Depreciation and amortization	5,829	5,428	11,264	11,062
Operating Segments | In-Center
Segment Reporting Information [Line Items]
Revenues	16,389	14,326	33,746	29,932
Segment profit (loss)	2,436	1,662	4,735	4,021
Depreciation and amortization	463	544	951	1,069
Operating Segments | Services
Segment Reporting Information [Line Items]
Revenues	5,184	4,857	10,603	9,907
Segment profit (loss)	(5,867)	(6,493)	(11,426)	(12,098)
Depreciation and amortization	1,319	1,302	2,662	2,570
Other
Segment Reporting Information [Line Items]
Revenues	2,522	2,836	5,342	5,735
Segment profit (loss)	(20,458)	(18,582)	(40,083)	(36,843)
Depreciation and amortization	1,077	1,092	2,161	2,164
Intersegment Elimination
Segment Reporting Information [Line Items]
Revenues	(1,205)	(1,261)	(2,390)	(2,648)
Segment profit (loss)	35	(17)	70	(39)
Depreciation and amortization	(46)	5	(92)	(27)
Intersegment Elimination | System One
Segment Reporting Information [Line Items]
Revenues	$ 1,205	$ 1,261	$ 2,390	$ 2,648

Segment Disclosures - Summary53

Segment Disclosures - Summary of Customers Who Individually Make Up Greater than 10% of Total Revenues (Details) - Sales Revenue, Net - Customer Concentration Risk	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
DaVita
Revenue, Major Customer [Line Items]
Percentage of revenues	19.00%	20.00%	19.00%	20.00%
Fresenius
Revenue, Major Customer [Line Items]
Percentage of revenues	21.00%	20.00%	20.00%	19.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Contingency [Line Items]
Benefit from income taxes	$ (372,000)	$ 22,000	$ (636,000)	$ 635,000
Allocation adjustments, amount	100,000	400,000	100,000	$ 1,300,000
Liability for unrecognized tax benefits	900,000		900,000
Interest and penalties accrued	100,000		100,000
Interest and penalties accrued during period	$ 0		$ 0
Maximum
Income Tax Contingency [Line Items]
Benefit from income taxes		$ 100,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expense in Consolidated Statements of Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,280	$ 2,750	$ 4,977	$ 5,324
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	220	263	471	567
Selling and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	749	1,137	1,576	1,993
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	311	334	693	717
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,000	$ 1,016	$ 2,237	$ 2,047

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, grants in period (in shares)	0	130,430	0	667,878
Weighted-average fair value of options granted (in dollars per share)				$ 9.94
Options to purchase common stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		1 year		1 year
Options to purchase common stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years		4 years
Unvested restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, grants in period (in shares)	0	21,737	0	154,925
Weighted-average grant date fair value (in dollars per share)				$ 27.69
Unvested restricted stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		3 years		3 years
Unvested restricted stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years		4 years

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Equity [Abstract]
Shares delivered or surrendered in payment for the exercise of stock options (in shares)	36,143	88,939

Noncontrolling Interest - Addit

Noncontrolling Interest - Additional Information (Details) $ in Thousands	Jun. 30, 2018USD ($)entity	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
Noncontrolling Interest [Abstract]
Number of VIEs | entity	5
Total assets of variable interest entities	$ 7,300		$ 5,600
Total liabilities and noncontrolling interest of variable interest entities	8,200		5,800
Noncontrolling interests subject to put provisions	$ (197)	$ (116)	$ (165)

Noncontrolling Interest - Sched

Noncontrolling Interest - Schedule of Changes in Noncontrolling Interest (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Balance at beginning of period	$ 273	$ 297	$ (12)	$ 625
Adjustment due to adoption of ASC 606					$ (25)	$ 542	$ 0	$ 0
Net loss attributable to noncontrolling interest in consolidated subsidiary	393	(442)	111	(770)
Balance at end of period	$ 641	$ (145)	$ 641	$ (145)

Derivative Instruments and He60

Derivative Instruments and Hedging - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Hedging Transactions And Derivative Financial Instruments [Line Items]
Period of cash flow hedges (up to)	12 months
Gain (loss) on ineffectiveness in earnings	$ 0	$ 0
Foreign exchange forward contracts | Cash Flow Hedges
Hedging Transactions And Derivative Financial Instruments [Line Items]
Notional amount of outstanding contracts	25.5		$ 24.1
Fair value of outstanding contracts liability	$ (0.3)
Fair value of outstanding contracts assets			$ 0.1

Derivative Instruments and He61

Derivative Instruments and Hedging - Effect of Contracts Designated as Cash Flow Hedges on Consolidated Financial Statements (Details) - Foreign exchange forward contracts - Cost of revenues - Cash Flow Hedges - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI (Effective Portion)	$ (535)	$ 1,563	$ 819	$ 4,095
Gain (Loss) Reclassified from OCI into Income (Effective Portion)	$ 421	$ 121	$ 975	$ (480)

Accumulated Other Comprehensi62

Accumulated Other Comprehensive (Loss) Income - Summary of Additional Information on Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance, net of tax			$ 213,146
Total other comprehensive (loss) income	$ (2,064)	$ 1,694	(905)	$ 4,599
Ending balance, net of tax	221,467		221,467
U.S. tax expense allocated to OCI			206
Unrealized gain (loss) on derivative instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance, net of tax			(1,284)
Other comprehensive income (loss) before reclassifications, net of $206 tax during 2018			614
Gain reclassified to earnings			(975)
Total other comprehensive (loss) income			(361)
Ending balance, net of tax	(1,645)		(1,645)
Other
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance, net of tax			(2,389)
Other comprehensive income (loss) before reclassifications, net of $206 tax during 2018			(544)
Gain reclassified to earnings			0
Total other comprehensive (loss) income			(544)
Ending balance, net of tax	(2,933)		(2,933)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance, net of tax			(3,673)
Other comprehensive income (loss) before reclassifications, net of $206 tax during 2018			70
Gain reclassified to earnings			(975)
Total other comprehensive (loss) income			(905)
Ending balance, net of tax	$ (4,578)		$ (4,578)

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value Measurements, Recurring Basis - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Foreign exchange forward contracts
Assets
Foreign exchange forward contracts	$ 261	$ 690
Liabilities
Foreign exchange forward contracts	545	661
Money market funds
Assets
Money market funds	35,248	35,020
Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign exchange forward contracts
Assets
Foreign exchange forward contracts	0	0
Liabilities
Foreign exchange forward contracts	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds
Assets
Money market funds	35,248	35,020
Significant Other Observable Inputs (Level 2) | Foreign exchange forward contracts
Assets
Foreign exchange forward contracts	261	690
Liabilities
Foreign exchange forward contracts	545	661
Significant Other Observable Inputs (Level 2) | Money market funds
Assets
Money market funds	0	0
Significant Unobservable Inputs (Level 3) | Foreign exchange forward contracts
Assets
Foreign exchange forward contracts	0	0
Liabilities
Foreign exchange forward contracts	0	0
Significant Unobservable Inputs (Level 3) | Money market funds
Assets
Money market funds	$ 0	$ 0

Fair Value Measurements Additio

Fair Value Measurements Additional Details (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Investment not readily marketable, fair value	$ 2.5	$ 2.5

Supplemental Cash Flow Inform65

Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Noncash Investing and Financing Activities:
Transfers from inventory to field equipment	$ 10,912	$ 10,254
Transfers from field equipment to deferred cost of revenues	7,770	4,983
Market value of shares received in payment for exercise of stock options	887	2,524
PP&E financed by construction liability	$ 95	$ 109