Insmed (INSM) 10-Q 30 Oct 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 26, 2018
Document and Entity Information
Entity Registrant Name	INSMED INC
Entity Central Index Key	1,104,506
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		77,090,229
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3

Consolidated Balance Sheets (un

Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 567,574	$ 381,165
Prepaid expenses and other current assets	9,921	8,279
Total current assets	577,495	389,444
Intangible assets	59,941	58,200
Fixed assets, net	19,526	12,432
Other assets	4,551	1,971
Total assets	661,513	462,047
Current liabilities:
Accounts payable	16,579	14,671
Accrued expenses	40,368	29,339
Other current liabilities	472	646
Total current liabilities	57,419	44,656
Long-term debt, net	311,861	55,567
Other long-term liabilities	826	765
Total liabilities	370,106	100,988
Shareholders’ equity:
Common stock, $0.01 par value; 500,000,000 authorized shares, 77,085,715 and 76,610,508 issued and outstanding shares at September 30, 2018 and December 31, 2017, respectively	771	766
Additional paid-in capital	1,481,205	1,318,181
Accumulated deficit	(1,190,589)	(957,885)
Accumulated other comprehensive income (loss)	20	(3)
Total shareholders’ equity	291,407	361,059
Total liabilities and shareholders’ equity	$ 661,513	$ 462,047

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	500,000,000	500,000,000
Common stock, issued shares (in shares)	77,085,715	76,610,508
Common stock, outstanding shares (in shares)	77,085,715	76,610,508

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Revenues	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	39,538	26,675	105,358	75,800
General and administrative	44,445	17,408	114,258	47,767
Total operating expenses	83,983	44,083	219,616	123,567
Operating loss	(83,983)	(44,083)	(219,616)	(123,567)
Investment income	2,741	326	7,510	649
Interest expense	(6,675)	(1,496)	(18,805)	(4,459)
Loss on extinguishment of debt	0	0	(2,209)	0
Other income, net	220	101	550	206
Loss before income taxes	(87,697)	(45,152)	(232,570)	(127,171)
Provision for income taxes	46	27	134	94
Net loss	$ (87,743)	$ (45,179)	$ (232,704)	$ (127,265)
Basic and diluted net loss per share (in dollars per share)	$ (1.14)	$ (0.69)	$ (3.03)	$ (2.01)
Weighted average basic and diluted common shares outstanding (in shares)	77,066	65,312	76,819	63,199
Net loss	$ (87,743)	$ (45,179)	$ (232,704)	$ (127,265)
Other comprehensive income:
Foreign currency translation gains	2	76	23	99
Total comprehensive loss	$ (87,741)	$ (45,103)	$ (232,681)	$ (127,166)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net loss	$ (232,704)	$ (127,265)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,652	2,168
Stock-based compensation expense	20,205	13,332
Amortization of debt issuance costs	1,000	91
Accretion of debt discount	11,541	0
Accretion of back-end fee on debt	50	506
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(4,315)	(1,052)
Accounts payable	2,536	(921)
Accrued expenses and other	10,596	1,745
Net cash used in operating activities	(188,439)	(111,396)
Investing activities
Purchase of fixed assets	(10,063)	(1,301)
Net cash used in investing activities	(10,063)	(1,301)
Financing activities
Proceeds from exercise of stock options	6,390	2,953
Loss on extinguishment of debt	(2,209)	0
Payment of debt	(55,000)	0
Proceeds from issuance of 1.75% convertible senior notes due 2025	450,000	0
Payment of debt issuance costs	(14,235)	0
Proceeds from issuance of common stock, net	0	377,703
Net cash provided by financing activities	384,946	380,656
Effect of exchange rates on cash and cash equivalents	(35)	128
Net increase in cash and cash equivalents	186,409	268,087
Cash and cash equivalents at beginning of period	381,165	162,591
Cash and cash equivalents at end of period	567,574	430,678
Supplemental disclosures of cash flow information:
Cash paid for interest	4,975	3,876
Cash paid for income taxes	$ 127	$ 62

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (unaudited) (Parenthetical)	Sep. 30, 2018
Convertible Notes | 1.75 convertible senior notes due 2025
Interest rate (as a percent)	1.75%

The Company and Basis of Presen

The Company and Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Basis of Presentation	The Company and Basis of Presentation Insmed is a global biopharmaceutical company on a mission to transform the lives of patients with serious and rare diseases. The Company's first commercial product, ARIKAYCE (amikacin liposome inhalation suspension), received accelerated approval in the United States (US) on September 28, 2018 for the treatment of Mycobacterium avium complex (MAC) lung disease as part of a combination antibacterial drug regimen for adult patients with limited or no alternative treatment options. MAC lung disease is a rare and often chronic infection that can cause irreversible lung damage and can be fatal. The Company's clinical-stage pipeline includes INS1007 and INS1009. INS1007 is a novel oral, reversible inhibitor of dipeptidyl peptidase 1 (DPP1) with therapeutic potential in non-cystic fibrosis (non-CF) bronchiectasis and other inflammatory diseases. INS1009 is an inhaled formulation of a treprostinil prodrug that may offer a differentiated product profile for rare pulmonary disorders, including pulmonary arterial hypertension (PAH). The Company was incorporated in the Commonwealth of Virginia on November 29, 1999 and its principal executive offices are in Bridgewater, New Jersey. The Company has legal entities in the US, Ireland, Germany, France, the United Kingdom (UK), the Netherlands, and Japan. All intercompany transactions and balances have been eliminated in consolidation. The accompanying unaudited interim consolidated financial statements have been prepared pursuant to the rules and regulations for reporting on Form 10-Q. Accordingly, certain information and disclosures required by accounting principles generally accepted in the US for complete consolidated financial statements are not included herein. The unaudited interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . The results of operations of any interim period are not necessarily indicative of the results of operations for the full year. The unaudited interim consolidated financial information presented herein reflects all normal adjustments that are, in the opinion of management, necessary for a fair statement of the financial position, results of operations and cash flows for the periods presented. The Company had $567.6 million in cash and cash equivalents as of September 30, 2018 and reported a net loss of $232.7 million for the nine months ended September 30, 2018 . Historically, the Company has funded its operations through public offerings of equity securities and debt financings. To date, the Company has not generated material revenue from ARIKAYCE. The Company commenced commercial shipments in October 2018. The Company expects to continue to incur operating losses while funding commercial launch efforts for ARIKAYCE, research and development (R&D) activities, regulatory submissions outside the US, and general and administrative expenses. The Company expects its future cash requirements to be substantial, and the Company may need to raise additional capital to fund operations, including the commercialization of ARIKAYCE and additional clinical trials related to ARIKAYCE, to develop INS1007 and INS1009 and to develop, acquire, in-license or co-promote other products that address orphan or rare diseases.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The following are the required interim disclosure updates to the Company's significant accounting policies described in Note 2 of the notes to the consolidated financial statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 : Fair Value Measurements - The Company categorizes its financial assets and liabilities measured and reported at fair value in the financial statements on a recurring basis based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels, which are directly related to the amount of subjectivity associated with the inputs used to determine the fair value of financial assets and liabilities, are as follows: • Level 1 — Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. • Level 2 — Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the assets or liability through correlation with market data at the measurement date and for the duration of the instrument’s anticipated life. • Level 3 — Inputs reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. Each major category of financial assets and liabilities measured at fair value on a recurring basis is categorized based upon the lowest level of significant input to the valuations. The fair value hierarchy also requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. Financial instruments in Level 1 generally include US treasuries and mutual funds listed in active markets. The Company’s only financial assets and liabilities which were measured at fair value as of September 30, 2018 and December 31, 2017 were Level 1 assets comprised of cash and cash equivalents of $567.6 million and $381.2 million , respectively. The estimated fair value of the liability component of the 1.75% convertible senior notes due 2025 (the Convertible Notes) (categorized as a Level 2 liability for fair value measurement purposes) was determined using current market factors and the ability of the Company to obtain debt on comparable terms to the Convertible Notes. The following table shows certain assets and liabilities and their carrying values and fair values: As of September 30, 2018 Carrying Value Fair Value (in millions) Level 1 Cash and cash equivalents $ 567.6 $ 567.6 Level 2 Convertible Notes ($450.0 face value) $ 311.9 * $ 381.6 * The carrying value of the Convertible Notes excludes $129.4 million of the unamortized portion of the debt discount. The Company’s cash and cash equivalents permit daily redemption and the fair values of these investments are based upon the quoted prices in active markets provided by the holding financial institutions. Cash equivalents consist of liquid investments with an original maturity of three months or less from the date of purchase. As of September 30, 2018 , the Company's cash and cash equivalents balance included US treasury bills of $399.8 million . The Company recognizes transfers between levels within the fair value hierarchy, if any, at the end of each quarter. There were no transfers in or out of Level 1, Level 2 or Level 3 during the nine months ended September 30, 2018 and 2017 , respectively. As of September 30, 2018 and December 31, 2017 , the Company held no securities that were in an unrealized gain or loss position. The Company reviews the status of each security quarterly to determine whether an other-than-temporary impairment has occurred. In making its determination, the Company considers a number of factors, including: (1) the significance of the decline; (2) whether the securities were rated below investment grade; (3) how long the securities have been in an unrealized loss position; and (4) the Company’s ability and intent to retain the investment for a sufficient period of time for it to recover. Net Loss Per Share - Basic net loss per share is computed by dividing net loss by the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted average number of common shares and other dilutive securities outstanding during the period. Potentially dilutive securities from stock options, restricted stock units (RSUs) and convertible debt securities would be anti-dilutive as the Company incurred a net loss. Potentially dilutive common shares resulting from the assumed exercise of outstanding stock options and from the assumed conversion of the Convertible Notes are determined based on the treasury stock method. The following table sets forth the reconciliation of the weighted average number of common shares used to compute basic and diluted net loss per share for the three and nine months ended September 30, 2018 and 2017 : Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands, except per share amounts) Numerator: Net loss $ (87,743 ) $ (45,179 ) $ (232,704 ) $ (127,265 ) Denominator: Weighted average common shares used in calculation of basic net loss per share: 77,066 65,312 76,819 63,199 Effect of dilutive securities: Common stock options — — — RSUs — — — Convertible debt securities — — — — Weighted average common shares outstanding used in calculation of diluted net loss per share 77,066 65,312 76,819 63,199 Net loss per share: Basic and diluted $ (1.14 ) $ (0.69 ) $ (3.03 ) $ (2.01 ) The following potentially dilutive securities have been excluded from the computations of diluted weighted average common shares outstanding as of September 30, 2018 and 2017 as their effect would have been anti-dilutive (in thousands): As of September 30, 2018 2017 Stock options to purchase common stock 9,608 8,601 Unvested RSUs 245 47 Convertible debt securities 11,492 — Inventory - Inventory is stated at the lower of cost and net realizable value with cost determined on a standard costing method. The Company began capitalizing inventory costs subsequent to US Food and Drug Administration (FDA) approval of ARIKAYCE on September 28, 2018, when it was determined that the inventory had a probable future economic benefit. Inventory will be sold beginning in the fourth quarter of 2018 based on first-in, first out basis. Manufacturing variances, such as material usage variance and yield variance, will be capitalized in inventory until the respective units are sold at which point the variances will be released in cost of goods sold. The Company will periodically review inventory for expiry and obsolescence and write down accordingly. The Company performs quality control procedures throughout the manufacturing processes of ARIKAYCE; however, certain batches or units of ARIKAYCE may not meet quality specifications and result in a charge to cost of goods sold. Prior to FDA approval of ARIKAYCE, the Company expensed all inventory related costs in the period incurred; therefore, inventory is not included in the September 30, 2018 consolidated balance sheet. Inventory used for clinical development purposes is expensed to research and development (R&D) expense when consumed. Recently Adopted Accounting Pronouncements - In August 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments , which addressed eight specific cash flow issues with the objective of reducing the existing diversity in practice. Among the updates, the standard requires debt extinguishment costs to be classified as cash outflows for financing activities. This standard update is effective as of the first quarter of 2018. As a result of the adoption of the standard, in the first quarter of 2018, the Company reported a $2.2 million loss on extinguishment of debt in the financing activities section of its consolidated statement of cash flows. The Company had no material debt extinguishment costs prior to the first quarter of 2018. The impact of adopting this standard was not material to the Company. New Accounting Pronouncements (Not Yet Adopted) —In February 2016, the FASB issued ASU 2016-2, Leases (Topic 842) in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under previous generally accepted accounting principles. ASU 2016-2 requires a lessee to recognize a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term on the balance sheet. ASU 2016-2 is effective for fiscal years beginning after December 15, 2018 (including interim periods within those periods) and early adoption is permitted. In August 2018, the FASB issued ASU 2018-11, Targeted Improvements to ASC 842

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	Intangible Assets As of September 30, 2018, the Company's identifiable intangible assets consisted of acquired ARIKAYCE R&D, formerly referred to as in-process research and development, and a milestone payable to PARI Pharma GmbH (PARI) for the license to use PARI's Lamira™ Nebulizer System for the delivery of ARIKAYCE to patients. The total carrying value of the acquired ARIKAYCE R&D was $58.2 million as of September 30, 2018 and December 31, 2017 , resulting from the initial amount recorded at the time of the Company's merger with Transave, Inc. (Transave) in 2010 and subsequent adjustments. On September 28, 2018, as a result of the FDA approval for ARIKAYCE, the Company recorded a milestone payment of $1.7 million due to PARI. Intangible assets consist of the following: As of September 30, As of December 31, (in thousands) Acquired ARIKAYCE R&D $ 58,200 $ 58,200 PARI milestone upon FDA approval 1,741 — Intangible assets $ 59,941 $ 58,200 Intangible assets are measured at their respective fair values on the date they were recorded and, with respect to the Acquired ARIKAYCE milestone, at the date of subsequent adjustments of fair value. Intangible assets will be amortized beginning October 1, 2018 over the initial regulatory exclusivity period for ARIKAYCE ( 12 years ). As of September 30, 2018

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses consist of the following: As of September 30, As of December 31, (in thousands) Accrued clinical trial expenses $ 6,576 $ 7,837 Accrued compensation 11,387 12,197 Accrued professional fees 10,746 4,500 Accrued technical operation expenses 5,137 2,182 Accrued milestone payment 1,741 — Accrued interest payable 1,663 423 Accrued construction costs 2,069 1,719 Other accrued expenses 1,049 481 $ 40,368 $ 29,339

Debt

Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	Debt In January 2018, the Company completed an underwritten public offering of the Convertible Notes, in which the Company sold $450.0 million aggregate principal amount of Convertible Notes, including the exercise in full of the underwriters' option to purchase additional Convertible Notes of $50.0 million . The Company's net proceeds from the offering, after deducting underwriting discounts and commissions and other offering expenses of $14.2 million , were approximately $435.8 million . The Convertible Notes bear interest payable semiannually in arrears on January 15 and July 15 of each year, beginning on July 15, 2018. The Convertible Notes mature on January 15, 2025, unless earlier converted, redeemed, or repurchased. On or after October 15, 2024, until the close of business on the second scheduled trading day immediately preceding January 15, 2025, holders may convert their Convertible Notes at any time. Upon conversion, holders may receive cash, shares of the Company's common stock or a combination of cash and shares of the Company's common stock, at the Company's option. The initial conversion rate is 25.5384 shares of common stock per $1,000 principal amount of Convertible Notes (equivalent to an initial conversion price of approximately $39.16 per share of common stock). The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. Holders may convert their Convertible Notes prior to October 15, 2024, only under the following circumstances, subject to the conditions set forth in an indenture, dated as of January 26, 2018, between the Company and Wells Fargo Bank, National Association (Wells Fargo), as trustee, as supplemented by the first supplemental indenture, dated January 26, 2018, between the Company and Wells Fargo (as supplemented, the Indenture): (i) during the five business day period immediately after any five consecutive trading day period (the measurement period) in which the trading price per $1,000 principal amount of convertible notes, as determined following a request by a holder of the convertible notes, for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the common stock and the conversion rate on such trading day, (ii) the Company elects to distribute to all or substantially all holders of the common stock (a) any rights, options or warrants (other than in connection with a stockholder rights plan for so long as the rights issued under such plan have not detached from the associated shares of common stock) entitling them, for a period of not more than 45 days from the declaration date for such distribution, to subscribe for or purchase shares of common stock at a price per share that is less than the average of the last reported sale prices of the common stock for the 10 consecutive trading day period ending on, and including, the trading day immediately preceding the declaration date for such distribution, or (b) the Company’s assets, debt securities or rights to purchase securities of the Company, which distribution has a per share value, as reasonably determined by the board of directors, exceeding 10% of the last reported sale price of the common stock on the trading day immediately preceding the declaration date for such distribution, (iii) if a transaction or event that constitutes a fundamental change or a make-whole fundamental change occurs, or if the Company is a party to (a) a consolidation, merger, combination, statutory or binding share exchange or similar transaction, pursuant to which the common stock would be converted into, or exchanged for, cash, securities or other property or assets, or (b) any sale, conveyance, lease or other transfer or similar transaction in one transaction or a series of transactions of all or substantially all of the consolidated assets of the Company and its subsidiaries, taken as a whole, all or any portion of the Convertible Notes may be surrendered by a holder for conversion at any time from or after the date that is 30 scheduled trading days prior to the anticipated effective date of the transaction, (iv) if during any calendar quarter commencing after the calendar quarter ending on March 31, 2018 (and only during such calendar quarter), the last reported sale price of the common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day, or, (v) if the Company sends a notice of redemption, a holder may surrender all or any portion of its Convertible Notes, to which the notice of redemption relates, for conversion at any time on or after the date the applicable notice of redemption was sent until the close of business on (a) the second business day immediately preceding the related redemption date or (b) if the Company fails to pay the redemption price on the redemption date as specified in such notice of redemption, such later date on which the redemption price is paid. The Convertible Notes can be settled in cash, common stock, or a combination of cash and common stock at the Company's option, and thus, the Company determined the embedded conversion options in the convertible notes are not required to be separately accounted for as a derivative. However, since the Convertible Notes are within the scope of the accounting guidance for cash convertible instruments, the Company is required to separate the Convertible Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated equity component. The fair value was based on data from readily available pricing sources which utilize market observable inputs and other characteristics for similar types of instruments. The carrying amount of the equity component representing the embedded conversion option was determined by deducting the fair value of the liability component from the gross proceeds of the Convertible Notes. The excess of the principal amount of the liability component over its carrying amount is amortized to interest expense over the expected life of a similar liability that does not have an associated equity component using the effective interest method. The equity component is not remeasured as long as it continues to meet the conditions for equity classification in the accounting guidance for contracts in an entity’s own equity. The fair value of the liability component of the Convertible Notes on the date of issuance was estimated at $309.1 million using an effective interest rate of 7.6% , and accordingly, the residual equity component on the date of issuance was $140.9 million . The discount is being amortized to interest expense over the term of the Convertible Notes and has a remaining period of approximately 6.28 years . For the three and nine months ended September 30, 2018 , total interest expense related to the Convertible Notes was $6.7 million and $17.9 million , respectively, which includes the contractual interest coupon payable semi-annually in cash, the amortization of the issuance costs, and accretion of debt discount, as described in the table below. The following table presents the carrying value of the Company’s debt balance as of September 30, 2018 (in thousands): 1.75% convertible senior notes due 2025 $ 450,000 Debt issuance costs, unamortized (8,789 ) Discount on debt (129,350 ) Long-term debt, net $ 311,861 As of September 30, 2018 , future principal repayments of the debt for each of the fiscal years through maturity were as follows (in thousands): Year Ending December 31: 2018 $ — 2019 — 2020 — 2021 — 2022 — 2023 and thereafter 450,000 $ 450,000 In February 2018, the Company used part of the net proceeds from the issuance of the Convertible Notes to pay off its outstanding debt to Hercules Capital (Hercules). The payments to Hercules consisted of $55.0 million for the principal amount and an additional $3.2 million in back-end fees, outstanding interest, and prepayment penalty fees, which resulted in a $2.2 million loss on extinguishment of debt in the quarter ended March 31, 2018. Interest Expense The following table sets forth the total interest expense recognized in the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Contractual interest expense $ 1,971 $ 1,302 $ 6,214 $ 3,862 Amortization of debt issuance costs 415 30 1,000 91 Accretion of back-end fee on debt — 164 50 506 Accretion of debt discount 4,289 — 11,541 — Total interest expense $ 6,675 $ 1,496 $ 18,805 $ 4,459

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Shareholders' Equity	Shareholders’ Equity Common Stock — As of September 30, 2018 , the Company had 500,000,000 shares of common stock authorized with a par value of $0.01 per share and 77,085,715 shares of common stock issued and outstanding. In addition, as of September 30, 2018 , the Company had reserved 9,608,344 shares of common stock for issuance upon the exercise of outstanding stock options and 244,801 shares of common stock for issuance upon the vesting of RSUs. The Company has also reserved 11,492,280 shares of common stock for issuance upon conversion of the Convertible Notes, subject to adjustment in accordance with the Indenture. In January 2018, the Company completed an underwritten public offering of $450.0 million aggregate principal amount of Convertible Notes, including the exercise in full of the underwriter's option to purchase additional Convertible Notes. The fair value of the liability component of the Convertible Notes on the date of issuance was estimated at $309.1 million , and accordingly, the equity component (included in additional paid-in capital) on the date of issuance was calculated as $140.9 million using the residual method, as further described in Note 5 Debt . In September 2017, the Company completed an underwritten public offering of 14,123,150 shares of the Company’s common stock, which included the underwriter’s exercise in full of its over-allotment option of 1,842,150 shares, at a price to the public of $28.50 per share. The Company’s net proceeds from the sale of the shares, after deducting the underwriter’s discount and offering expenses of $24.8 million , were $ 377.7 million . Preferred Stock — As of September 30, 2018 , the Company had 200,000,000 shares of preferred stock authorized with a par value of $0.01 per share and no shares of preferred stock were issued and outstanding. The following table summarizes the changes in total shareholders' equity for the nine months ended September 30, 2018 (in thousands): Balance at December 31, 2017 $ 361,059 Net loss for the period (232,704 ) Proceeds from exercise of stock options 6,390 Equity component of Convertible Notes 136,434 Stock-based compensation expense 20,205 Change in cumulative translation adjustment 23 Balance at September 30, 2018 $ 291,407

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Company’s current equity compensation plan, the 2017 Incentive Plan, was approved by shareholders at the Company’s Annual Meeting of Shareholders on May 18, 2017. The 2017 Incentive Plan is administered by the Compensation Committee and the Board of Directors of the Company. Under the terms of the 2017 Incentive Plan, the Company is authorized to grant a variety of incentive awards based on its common stock, including stock options (both incentive stock options and non-qualified stock options), RSUs, performance options/shares and other stock awards, as well as pay incentive bonuses to eligible employees and non-employee directors. On May 18, 2017, upon the approval of the 2017 Incentive Plan by shareholders, 5,000,000 shares were authorized for issuance thereunder, plus any shares subject to then-outstanding awards under the 2015 Incentive Plan and the 2013 Incentive Plan that subsequently were canceled, terminated unearned, expired, were forfeited, lapsed for any reason or were settled in cash without the delivery of shares. As of September 30, 2018 , 3,408,995 shares remained for future issuance under the 2017 Incentive Plan. The 2017 Incentive Plan will terminate on April 3, 2027 unless it is extended or terminated earlier pursuant to its terms. In addition, from time to time, the Company makes inducement grants of stock options to new hires, which awards are made pursuant to the NASDAQ inducement grant exception. During the nine months ended September 30, 2018 , the Company granted inducement stock options covering 236,730 shares of the Company's common stock to new employees. On May 15, 2018, the 2018 Employee Stock Purchase Plan (2018 ESPP) was approved by shareholders at the Company’s Annual Meeting of Shareholders. The Company has reserved the following for issuance under the 2018 ESPP: (i) 1,000,000 shares of common stock, plus (ii) commencing on January 1, 2019 and ending on December 31, 2023, an additional number of shares to be added on the first day of each calendar year equal to the lesser of (A) 1,200,000 shares of common stock, (B) 2% of the number of outstanding shares of common stock on such date and (C) an amount determined by the administrator. Stock Options - The Company calculates the fair value of stock options granted using the Black-Scholes valuation model. The following table summarizes the Company’s grant date fair value and assumptions used in determining the fair value of all stock options granted during the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Volatility 66%-67% 72%-73% 66%-68% 72%-74% Risk-free interest rate 2.75%-2.87% 1.73%-1.93% 2.25%-2.87% 1.73%-1.99% Dividend yield 0.0% 0.0% 0.0% 0.0% Expected option term (in years) 5.14 6.25 5.09 6.25 Weighted average fair value of stock options granted $13.62 $9.59 $16.56 $10.18 For each period presented, the volatility factor was based on the Company’s historical volatility during the expected option term. Estimated forfeitures are based on the actual percentage of option forfeitures since the closing of the Company’s merger with Transave in December 2010. The expected option term for these grants was determined using the Company’s historical exercise behavior of grantees. From time to time, the Company has granted performance-condition options to certain of its employees. Vesting of these options was subject to the Company achieving certain performance criteria established at the date of grant and the grantees fulfilling a service condition (continued employment). During the quarter ended September 30, 2018 , performance-condition options totaling $1.1 million , or 133,334 shares, met their recognition criteria as a result of the FDA approval of ARIKAYCE and vested in full. As of September 30, 2018 , there were no performance-condition options outstanding. The following table summarizes the Company’s aggregate stock option activity for the nine months ended September 30, 2018 : Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value (in thousands) Options outstanding at December 31, 2017 8,608,921 $ 14.08 Granted 1,610,010 $ 28.57 Exercised (427,729 ) $ 14.94 Forfeited or expired (182,858 ) $ 19.15 Options outstanding at September 30, 2018 9,608,344 $ 16.37 7.08 $ 52,765 Vested and expected to vest at September 30, 2018 8,760,828 $ 15.90 6.92 $ 50,354 Exercisable at September 30, 2018 5,317,732 $ 13.23 5.96 $ 38,723 The total intrinsic value of stock options exercised during the three months ended September 30, 2018 and 2017 was $0.6 million and $1.4 million , respectively, and during the nine months ended September 30, 2018 and 2017 was $5.5 million and $3.5 million , respectively. As of September 30, 2018 , there was $34.7 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted average period of 2.5 years . The following table summarizes the range of exercise prices and the number of stock options outstanding and exercisable as of September 30, 2018 : Outstanding as of September 30, 2018 Exercisable as of September 30, 2018 Range of Exercise Prices ($) Number of Options Weighted Average Remaining Contractual Term (in years) Weighted Average Exercise Price ($) Number of Options Weighted Average Exercise Price ($) $ 3.03 $ 6.90 1,087,941 3.94 $ 3.99 1,087,941 $ 3.99 $ 6.96 $ 10.85 997,221 7.53 $ 10.77 481,574 $ 10.68 $ 11.14 $ 12.58 984,936 5.49 $ 12.17 893,989 $ 12.20 $ 12.66 $ 13.67 984,161 7.97 $ 13.60 428,577 $ 13.56 $ 13.94 $ 16.07 1,139,533 6.80 $ 15.26 765,384 $ 15.17 $ 16.09 $ 17.16 1,438,502 7.95 $ 16.69 602,949 $ 16.48 $ 17.24 $ 22.76 1,366,680 6.56 $ 21.20 1,017,263 $ 21.26 $ 22.84 $ 30.46 1,439,910 9.21 $ 28.61 40,055 $ 24.26 $ 30.86 $ 31.78 155,960 9.25 $ 31.10 — $ — $ 32.46 $ 32.46 13,500 9.26 $ 32.46 — $ — Restricted Stock and Restricted Stock Units — Under the 2017 Incentive Plan, the Company may grant restricted stock (RS) and RSUs to eligible participants, including its executives, non-employee directors, and other service providers. Each share of RS vests, and each RSU represents a right to receive one share of the Company’s common stock, upon the completion of a specific period of continued service or achievement of a certain milestone. RS and RSU awards are valued at the market price of the Company’s common stock on the date of grant. The Company recognizes noncash compensation expense for the fair values of these RS and RSU awards on a straight-line basis over the requisite service period of these awards. As of September 30, 2018 , there was $4.2 million of unrecognized compensation expense related to unvested RSU awards which is expected to be recognized over a weighted average period of 2.8 years . The following table summarizes the Company’s RSU award activity during the nine months ended September 30, 2018 : Number of RSUs Weighted Average Grant Price ($) Outstanding at December 31, 2017 46,914 $ 17.16 Granted 248,468 $ 29.41 Released (47,478 ) $ 17.32 Forfeited (3,103 ) $ 30.46 Outstanding at September 30, 2018 244,801 $ 29.40 The following table summarizes the aggregate stock-based compensation expense recorded in the consolidated statements of comprehensive loss related to stock options and RSUs during the three and nine months ended September 30, 2018 and 2017 , respectively: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in millions) Research and development expenses $ 2.8 $ 1.8 $ 7.4 $ 4.8 General and administrative expenses 5.1 2.9 12.8 8.5 Total $ 7.9 $ 4.7 $ 20.2 $ 13.3

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company’s provision for income taxes was $ 46,000 and $ 134,000 for the three and nine months ended September 30, 2018 , respectively, and $ 27,000 and $ 94,000 for the three and nine months ended September 30, 2017 , respectively. The provision for income taxes in all periods was a result of certain of the Company’s subsidiaries in Europe, which had taxable income during the three and nine months ended September 30, 2018 and 2017 . In jurisdictions where the Company has net losses, there was a full valuation allowance recorded against the Company’s deferred tax assets and therefore no tax benefit was recorded. Following adoption of the Tax Cuts and Jobs Act during the fourth quarter of 2017, the Company remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. The Company recorded a provisional amount of $94.0 million as of December 31, 2017 related to the re-measurement of certain deferred tax balances, which was completely offset by a full valuation allowance. Upon further analyses, the Company determined in the second quarter of 2018 that the provisional amount would not need to be adjusted. In addition to local taxes in foreign jurisdictions, the Company is subject to US federal, US state, and US tax on foreign earnings. In regard to the US tax on foreign earnings, the Company was subject to a one-time transition tax based on its total earnings and profits, which were generally deferred from US income taxes under previous US law. Due to the aggregate loss position of the Company's foreign subsidiaries, the Company did not record any provisional amount for the one-time transition tax liability at December 31, 2017. Additionally, the global intangible low-taxed income tax and base erosion provisions in the Tax Cuts and Jobs Act are effective for taxable years beginning after December 31, 2017. The Company does not currently expect these provisions to have a material impact (i) due to the aggregate loss position of its foreign subsidiaries and (ii) because the Company currently expects to be below the gross receipts threshold for purposes of the base erosion provisions. The Company is subject to US federal and state income taxes and the statute of limitations for tax audit is open for the Company's federal tax returns for the years ended 2014 and later, and is generally open for certain states for the years 2013 and later. The Company has incurred net operating losses since inception, except for the year ended December 31, 2009. Such loss carryforwards would be subject to audit in any tax year in which those losses are utilized, notwithstanding the year of origin. As of September 30, 2018 and December 31, 2017 , the Company had recorded no

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company has an operating lease for office and laboratory space located in Bridgewater, NJ, its corporate headquarters, for which the initial lease term expires in November 2019. Future minimum rental payments under this lease are $1.2 million . In July 2016, the Company signed an operating lease for laboratory space located in Bridgewater, NJ for which the initial lease term expires in December 2021. Future minimum rental payments under this lease are $1.5 million . In September 2018, the Company entered into a lease agreement for office space in Bridgewater, NJ for its future corporate headquarters. The lease provides for a commencement date of the earlier of (1) September 1, 2019, subject to completion of certain improvements by specified dates, and (2) the date on which the Company takes possession of the premises to commence its business operations therein (the Commencement Date). The initial lease term runs 130 months from the Commencement Date (plus any partial month from the Commencement Date until the first day of the next full calendar month during the term), and the Company has the option to extend that term for up to three additional five -year periods. Future minimum rental payments under this lease are $32.3 million . Rent expense charged to operations was $0.4 million and $0.4 million for the three months ended September 30, 2018 and 2017 , respectively, and $1.2 million and $1.1 million for the nine months ended September 30, 2018 and 2017 , respectively. Future minimum rental payments required under the Company’s leases for the period from October 1, 2018 to December 31, 2018 and for each of the five years thereafter are as follows (in thousands): Year Ending December 31: 2018 (remaining) $ 490 2019 3,863 2020 4,185 2021 3,958 2022 1,281 2023 and thereafter 23,261 $ 37,038 Legal Proceedings

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Fair Value Measurements	Fair Value Measurements - The Company categorizes its financial assets and liabilities measured and reported at fair value in the financial statements on a recurring basis based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels, which are directly related to the amount of subjectivity associated with the inputs used to determine the fair value of financial assets and liabilities, are as follows: • Level 1 — Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. • Level 2 — Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the assets or liability through correlation with market data at the measurement date and for the duration of the instrument’s anticipated life. • Level 3 — Inputs reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. Each major category of financial assets and liabilities measured at fair value on a recurring basis is categorized based upon the lowest level of significant input to the valuations. The fair value hierarchy also requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. Financial instruments in Level 1 generally include US treasuries and mutual funds listed in active markets. The Company’s only financial assets and liabilities which were measured at fair value as of September 30, 2018 and December 31, 2017 were Level 1 assets comprised of cash and cash equivalents of $567.6 million and $381.2 million , respectively. The estimated fair value of the liability component of the 1.75% convertible senior notes due 2025 (the Convertible Notes) (categorized as a Level 2 liability for fair value measurement purposes) was determined using current market factors and the ability of the Company to obtain debt on comparable terms to the Convertible Notes. The following table shows certain assets and liabilities and their carrying values and fair values: As of September 30, 2018 Carrying Value Fair Value (in millions) Level 1 Cash and cash equivalents $ 567.6 $ 567.6 Level 2 Convertible Notes ($450.0 face value) $ 311.9 * $ 381.6 * The carrying value of the Convertible Notes excludes $129.4 million of the unamortized portion of the debt discount. The Company’s cash and cash equivalents permit daily redemption and the fair values of these investments are based upon the quoted prices in active markets provided by the holding financial institutions. Cash equivalents consist of liquid investments with an original maturity of three months or less from the date of purchase. As of September 30, 2018 , the Company's cash and cash equivalents balance included US treasury bills of $399.8 million . The Company recognizes transfers between levels within the fair value hierarchy, if any, at the end of each quarter. There were no transfers in or out of Level 1, Level 2 or Level 3 during the nine months ended September 30, 2018 and 2017 , respectively. As of September 30, 2018 and December 31, 2017 , the Company held no
Net Loss Per Share	Net Loss Per Share - Basic net loss per share is computed by dividing net loss by the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted average number of common shares and other dilutive securities outstanding during the period. Potentially dilutive securities from stock options, restricted stock units (RSUs) and convertible debt securities would be anti-dilutive as the Company incurred a net loss. Potentially dilutive common shares resulting from the assumed exercise of outstanding stock options and from the assumed conversion of the Convertible Notes are determined based on the treasury stock method. The following table sets forth the reconciliation of the weighted average number of common shares used to compute basic and diluted net loss per share for the three and nine months ended September 30, 2018 and 2017 : Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands, except per share amounts) Numerator: Net loss $ (87,743 ) $ (45,179 ) $ (232,704 ) $ (127,265 ) Denominator: Weighted average common shares used in calculation of basic net loss per share: 77,066 65,312 76,819 63,199 Effect of dilutive securities: Common stock options — — — RSUs — — — Convertible debt securities — — — — Weighted average common shares outstanding used in calculation of diluted net loss per share 77,066 65,312 76,819 63,199 Net loss per share: Basic and diluted $ (1.14 ) $ (0.69 ) $ (3.03 ) $ (2.01 ) The following potentially dilutive securities have been excluded from the computations of diluted weighted average common shares outstanding as of September 30, 2018 and 2017 as their effect would have been anti-dilutive (in thousands): As of September 30, 2018 2017 Stock options to purchase common stock 9,608 8,601 Unvested RSUs 245 47 Convertible debt securities 11,492 —
Inventory	Inventory - Inventory is stated at the lower of cost and net realizable value with cost determined on a standard costing method. The Company began capitalizing inventory costs subsequent to US Food and Drug Administration (FDA) approval of ARIKAYCE on September 28, 2018, when it was determined that the inventory had a probable future economic benefit. Inventory will be sold beginning in the fourth quarter of 2018 based on first-in, first out basis. Manufacturing variances, such as material usage variance and yield variance, will be capitalized in inventory until the respective units are sold at which point the variances will be released in cost of goods sold. The Company will periodically review inventory for expiry and obsolescence and write down accordingly. The Company performs quality control procedures throughout the manufacturing processes of ARIKAYCE; however, certain batches or units of ARIKAYCE may not meet quality specifications and result in a charge to cost of goods sold. Prior to FDA approval of ARIKAYCE, the Company expensed all inventory related costs in the period incurred; therefore, inventory is not included in the September 30, 2018
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements - In August 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments , which addressed eight specific cash flow issues with the objective of reducing the existing diversity in practice. Among the updates, the standard requires debt extinguishment costs to be classified as cash outflows for financing activities. This standard update is effective as of the first quarter of 2018. As a result of the adoption of the standard, in the first quarter of 2018, the Company reported a $2.2 million loss on extinguishment of debt in the financing activities section of its consolidated statement of cash flows. The Company had no material debt extinguishment costs prior to the first quarter of 2018. The impact of adopting this standard was not material to the Company. New Accounting Pronouncements (Not Yet Adopted) —In February 2016, the FASB issued ASU 2016-2, Leases (Topic 842) in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under previous generally accepted accounting principles. ASU 2016-2 requires a lessee to recognize a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term on the balance sheet. ASU 2016-2 is effective for fiscal years beginning after December 15, 2018 (including interim periods within those periods) and early adoption is permitted. In August 2018, the FASB issued ASU 2018-11, Targeted Improvements to ASC 842 , which provides a new transition option in which an entity initially applies ASU 2016-2 at the adoption date and recognizes a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The Company will use the new transition option and is also utilizing the package of practical expedients that allows it to not reassess: (1) whether any expired or existing contracts are or contain leases, (2) lease classification for any expired or existing leases, and (3) initial direct costs for any expired or existing leases. The Company additionally expects to use the practical expedient that allows it to treat the lease and non-lease components of its leases as a single component. The Company has identified approximately ten leasing arrangements and is currently assessing the financial impact on the consolidated balance sheet. The Company expects to adopt ASU 2016-2 in the first quarter of 2019 and is in the process of evaluating the impact of adoption on its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Schedule of Carrying Value and Fair Value of Assets and Liabilities	The following table shows certain assets and liabilities and their carrying values and fair values: As of September 30, 2018 Carrying Value Fair Value (in millions) Level 1 Cash and cash equivalents $ 567.6 $ 567.6 Level 2 Convertible Notes ($450.0 face value) $ 311.9 * $ 381.6 * The carrying value of the Convertible Notes excludes $129.4 million
Reconciliation of the Weighted Average Number of Shares Used to Compute Basic and Diluted Net Loss per Share	The following table sets forth the reconciliation of the weighted average number of common shares used to compute basic and diluted net loss per share for the three and nine months ended September 30, 2018 and 2017 : Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands, except per share amounts) Numerator: Net loss $ (87,743 ) $ (45,179 ) $ (232,704 ) $ (127,265 ) Denominator: Weighted average common shares used in calculation of basic net loss per share: 77,066 65,312 76,819 63,199 Effect of dilutive securities: Common stock options — — — RSUs — — — Convertible debt securities — — — — Weighted average common shares outstanding used in calculation of diluted net loss per share 77,066 65,312 76,819 63,199 Net loss per share: Basic and diluted $ (1.14 ) $ (0.69 ) $ (3.03 ) $ (2.01 )
Potentially Dilutive Securities Excluded from Computations of Diluted Weighted Average Common Shares Outstanding	The following potentially dilutive securities have been excluded from the computations of diluted weighted average common shares outstanding as of September 30, 2018 and 2017 as their effect would have been anti-dilutive (in thousands): As of September 30, 2018 2017 Stock options to purchase common stock 9,608 8,601 Unvested RSUs 245 47 Convertible debt securities 11,492 —

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	Intangible assets consist of the following: As of September 30, As of December 31, (in thousands) Acquired ARIKAYCE R&D $ 58,200 $ 58,200 PARI milestone upon FDA approval 1,741 — Intangible assets $ 59,941 $ 58,200

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following: As of September 30, As of December 31, (in thousands) Accrued clinical trial expenses $ 6,576 $ 7,837 Accrued compensation 11,387 12,197 Accrued professional fees 10,746 4,500 Accrued technical operation expenses 5,137 2,182 Accrued milestone payment 1,741 — Accrued interest payable 1,663 423 Accrued construction costs 2,069 1,719 Other accrued expenses 1,049 481 $ 40,368 $ 29,339

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Components of Debt Balance	The following table presents the carrying value of the Company’s debt balance as of September 30, 2018 (in thousands): 1.75% convertible senior notes due 2025 $ 450,000 Debt issuance costs, unamortized (8,789 ) Discount on debt (129,350 ) Long-term debt, net $ 311,861
Schedule of Future Principal Repayments of Debt	As of September 30, 2018 , future principal repayments of the debt for each of the fiscal years through maturity were as follows (in thousands): Year Ending December 31: 2018 $ — 2019 — 2020 — 2021 — 2022 — 2023 and thereafter 450,000 $ 450,000
Summary of Interest Expense	The following table sets forth the total interest expense recognized in the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Contractual interest expense $ 1,971 $ 1,302 $ 6,214 $ 3,862 Amortization of debt issuance costs 415 30 1,000 91 Accretion of back-end fee on debt — 164 50 506 Accretion of debt discount 4,289 — 11,541 — Total interest expense $ 6,675 $ 1,496 $ 18,805 $ 4,459

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Schedule of Changes in Shareholders' Equity	The following table summarizes the changes in total shareholders' equity for the nine months ended September 30, 2018 (in thousands): Balance at December 31, 2017 $ 361,059 Net loss for the period (232,704 ) Proceeds from exercise of stock options 6,390 Equity component of Convertible Notes 136,434 Stock-based compensation expense 20,205 Change in cumulative translation adjustment 23 Balance at September 30, 2018 $ 291,407

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Fair Value Assumptions for Stock Options	The following table summarizes the Company’s grant date fair value and assumptions used in determining the fair value of all stock options granted during the periods presented: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Volatility 66%-67% 72%-73% 66%-68% 72%-74% Risk-free interest rate 2.75%-2.87% 1.73%-1.93% 2.25%-2.87% 1.73%-1.99% Dividend yield 0.0% 0.0% 0.0% 0.0% Expected option term (in years) 5.14 6.25 5.09 6.25 Weighted average fair value of stock options granted $13.62 $9.59 $16.56 $10.18
Summary of Stock Option Activity	The following table summarizes the Company’s aggregate stock option activity for the nine months ended September 30, 2018 : Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value (in thousands) Options outstanding at December 31, 2017 8,608,921 $ 14.08 Granted 1,610,010 $ 28.57 Exercised (427,729 ) $ 14.94 Forfeited or expired (182,858 ) $ 19.15 Options outstanding at September 30, 2018 9,608,344 $ 16.37 7.08 $ 52,765 Vested and expected to vest at September 30, 2018 8,760,828 $ 15.90 6.92 $ 50,354 Exercisable at September 30, 2018 5,317,732 $ 13.23 5.96 $ 38,723
Summary of Exercise Price and Number of Stock Options Exercisable	The following table summarizes the range of exercise prices and the number of stock options outstanding and exercisable as of September 30, 2018 : Outstanding as of September 30, 2018 Exercisable as of September 30, 2018 Range of Exercise Prices ($) Number of Options Weighted Average Remaining Contractual Term (in years) Weighted Average Exercise Price ($) Number of Options Weighted Average Exercise Price ($) $ 3.03 $ 6.90 1,087,941 3.94 $ 3.99 1,087,941 $ 3.99 $ 6.96 $ 10.85 997,221 7.53 $ 10.77 481,574 $ 10.68 $ 11.14 $ 12.58 984,936 5.49 $ 12.17 893,989 $ 12.20 $ 12.66 $ 13.67 984,161 7.97 $ 13.60 428,577 $ 13.56 $ 13.94 $ 16.07 1,139,533 6.80 $ 15.26 765,384 $ 15.17 $ 16.09 $ 17.16 1,438,502 7.95 $ 16.69 602,949 $ 16.48 $ 17.24 $ 22.76 1,366,680 6.56 $ 21.20 1,017,263 $ 21.26 $ 22.84 $ 30.46 1,439,910 9.21 $ 28.61 40,055 $ 24.26 $ 30.86 $ 31.78 155,960 9.25 $ 31.10 — $ — $ 32.46 $ 32.46 13,500 9.26 $ 32.46 — $ —
Summary of RSU Activity	The following table summarizes the Company’s RSU award activity during the nine months ended September 30, 2018 : Number of RSUs Weighted Average Grant Price ($) Outstanding at December 31, 2017 46,914 $ 17.16 Granted 248,468 $ 29.41 Released (47,478 ) $ 17.32 Forfeited (3,103 ) $ 30.46 Outstanding at September 30, 2018 244,801 $ 29.40
Summary of Allocation of Employee Stock-Based Compensation	The following table summarizes the aggregate stock-based compensation expense recorded in the consolidated statements of comprehensive loss related to stock options and RSUs during the three and nine months ended September 30, 2018 and 2017 , respectively: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in millions) Research and development expenses $ 2.8 $ 1.8 $ 7.4 $ 4.8 General and administrative expenses 5.1 2.9 12.8 8.5 Total $ 7.9 $ 4.7 $ 20.2 $ 13.3

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments Required Under Operating Leases	Future minimum rental payments required under the Company’s leases for the period from October 1, 2018 to December 31, 2018 and for each of the five years thereafter are as follows (in thousands): Year Ending December 31: 2018 (remaining) $ 490 2019 3,863 2020 4,185 2021 3,958 2022 1,281 2023 and thereafter 23,261 $ 37,038

The Company and Basis of Pres_2

The Company and Basis of Presentation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 567,574	$ 430,678	$ 567,574	$ 430,678	$ 381,165	$ 162,591
Net loss	$ 87,743	$ 45,179	$ 232,704	$ 127,265

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details)	9 Months Ended
	Sep. 30, 2018USD ($)security	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)security
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cash and cash equivalents	$ 567,600,000		$ 381,200,000
Fair value transfers in or out of Level 1, Level 2, or Level 3	$ 0	$ 0
Securities in an unrealized gain or loss position | security	0		0
Convertible Notes | 1.75 convertible senior notes due 2025
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Interest rate (as a percent)	1.75%
US treasury bills
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cash and cash equivalents	$ 399,800,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Fair Value Measurements (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cash and cash equivalents	$ 567,600,000	$ 381,200,000
Unamortized portion of debt discount	129,350,000
Convertible Notes
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Face amount	450,000,000
Unamortized portion of debt discount	129,400,000
Recurring basis | Carrying Value | Level 1
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cash and cash equivalents	567,600,000
Recurring basis | Carrying Value | Level 2
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Convertible Notes ($450.0 face value)	311,900,000
Recurring basis | Fair Value | Level 1
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Cash and cash equivalents	567,600,000
Recurring basis | Fair Value | Level 2
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Convertible Notes ($450.0 face value)	$ 381,600,000

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net loss	$ (87,743)	$ (45,179)	$ (232,704)	$ (127,265)
Denominator:
Weighted average common shares used in calculation of basic net loss per share (in shares)	77,066	65,312	76,819	63,199
Effect of dilutive securities:
Dilutive securities, convertible debt (in shares)	0	0	0	0
Weighted average common shares outstanding used in calculation of diluted net loss per share (in shares)	77,066	65,312	76,819	63,199
Net loss per share:
Basic and diluted (in dollars per share)	$ (1.14)	$ (0.69)	$ (3.03)	$ (2.01)
Common stock options
Effect of dilutive securities:
Dilutive securities, share-based payment (in shares)	0	0	0
RSUs
Effect of dilutive securities:
Dilutive securities, share-based payment (in shares)	0	0	0

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Anti-dilutive Securities (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Stock options to purchase common stock
Anti-dilutive securities excluded from computations of diluted weighted-average common shares outstanding
Potentially dilutive securities excluded from computations of diluted weighted-average shares outstanding	9,608	8,601
Unvested RSUs
Anti-dilutive securities excluded from computations of diluted weighted-average common shares outstanding
Potentially dilutive securities excluded from computations of diluted weighted-average shares outstanding	245	47
Convertible debt securities
Anti-dilutive securities excluded from computations of diluted weighted-average common shares outstanding
Potentially dilutive securities excluded from computations of diluted weighted-average shares outstanding	11,492	0

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Accounting Policies [Abstract]
Loss on extinguishment of debt	$ 2,200	$ 2,209	$ 0

Intangible Assets - Narrative (

Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 28, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 59,941		$ 58,200
Accrued milestone payment	$ 1,741	$ 1,700	0
Intangible assets estimated useful life	12 years
Acquired ARIKAYCE R&D
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 58,200		$ 58,200

Intangible Assets - Schedule of

Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 59,941	$ 58,200
Acquired ARIKAYCE R&D
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	58,200	58,200
PARI milestone upon FDA approval
Finite-Lived Intangible Assets [Line Items]
Intangible Assets	$ 1,741	$ 0

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 28, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued clinical trial expenses	$ 6,576		$ 7,837
Accrued compensation	11,387		12,197
Accrued professional fees	10,746		4,500
Accrued technical operation expenses	5,137		2,182
Accrued milestone payment	1,741	$ 1,700	0
Accrued interest payable	1,663		423
Accrued construction costs	2,069		1,719
Other accrued expenses	1,049		481
Total accrued expenses	$ 40,368		$ 29,339

Debt - Narrative (Details)

Debt - Narrative (Details)	Feb. 28, 2018USD ($)	Feb. 28, 2018USD ($)	Jan. 31, 2018USD ($)day$ / shares	Sep. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)
Debt Instrument [Line Items]
Underwriting discounts and commissions and other offering expenses				$ 8,789,000			$ 8,789,000
Interest expense				6,675,000		$ 1,496,000	18,805,000	$ 4,459,000
Repayment of debt							55,000,000	0
Loss on extinguishment of debt				0	$ 2,200,000	$ 0	2,209,000	$ 0
1.75 convertible senior notes due 2025
Debt Instrument [Line Items]
Net proceeds			$ 435,800,000
Initial conversion rate			0.0255384
A&R Loan Agreement with Hercules
Debt Instrument [Line Items]
Repayment of debt	$ 55,000,000
Repayment of debt, back end fees, outstanding interest, and prepayment penalty fees		$ 3,200,000
Convertible Notes
Debt Instrument [Line Items]
Aggregate principal amount				450,000,000			450,000,000
Convertible Notes | 1.75 convertible senior notes due 2025
Debt Instrument [Line Items]
Aggregate principal amount			$ 450,000,000
Option to purchase additional debt			50,000,000
Underwriting discounts and commissions and other offering expenses			$ 14,200,000
Initial conversion price (in dollars per share) | $ / shares			$ 39.16
Convertible Notes ($450.0 face value)			$ 309,100,000
Effective interest rate			7.60%
Equity component of convertible debt			$ 140,900,000
Remaining discount amortization period			6 years 3 months 10 days
Interest expense				$ 6,700,000			$ 17,900,000
Convertible Notes | Conversion Term (i) | 1.75 convertible senior notes due 2025
Debt Instrument [Line Items]
Threshold trading days | day			5
Threshold consecutive trading days | day			5
Threshold percent of stock price trigger			98.00%
Convertible Notes | Conversion Term (ii) | 1.75 convertible senior notes due 2025
Debt Instrument [Line Items]
Threshold trading days | day			45
Threshold consecutive trading days | day			10
Threshold percent of stock price trigger			10.00%
Convertible Notes | Conversion Term (iii) | 1.75 convertible senior notes due 2025
Debt Instrument [Line Items]
Threshold trading days following fundamental change | day			30
Convertible Notes | Conversion Term (iv) | 1.75 convertible senior notes due 2025
Debt Instrument [Line Items]
Threshold trading days | day			20
Threshold consecutive trading days | day			30
Threshold percent of stock price trigger			130.00%

Debt - Components of Debt (Deta

Debt - Components of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
1.75% convertible senior notes due 2025	$ 450,000
Debt issuance costs, unamortized	(8,789)
Discount on debt	(129,350)
Long-term debt, net	311,861		$ 55,567
Convertible Notes
Debt Instrument [Line Items]
Discount on debt	$ (129,400)
Convertible Notes | 1.75 convertible senior notes due 2025
Debt Instrument [Line Items]
Interest rate (as a percent)	1.75%
Debt issuance costs, unamortized		$ (14,200)

Debt - Future Principal Repayme

Debt - Future Principal Repayments of Debt (Details) $ in Thousands	Sep. 30, 2018USD ($)
Year Ending December 31:
2,018	$ 0
2,019	0
2,020	0
2,021	0
2,022	0
2023 and thereafter	450,000
Total	$ 450,000

Debt - Interest Expense (Detail

Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Debt Disclosure [Abstract]
Contractual interest expense	$ 1,971	$ 1,302	$ 6,214	$ 3,862
Amortization of debt issuance costs	415	30	1,000	91
Accretion of back-end fee on debt	0	164	50	506
Accretion of debt discount	4,289	0	11,541	0
Total interest expense	$ 6,675	$ 1,496	$ 18,805	$ 4,459

Shareholders' Equity - Narrativ

Shareholders' Equity - Narrative (Details) - USD ($)	1 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common stock, authorized shares (in shares)		500,000,000			500,000,000
Common stock, par value (in dollars per share)		$ 0.01			$ 0.01
Common stock, issued shares (in shares)		77,085,715			76,610,508
Common stock, outstanding shares (in shares)		77,085,715			76,610,508
Shares issued under underwritten public offering (in shares)	14,123,150
Shares exercised in full of over-allotment option by underwriter (in shares)	1,842,150		1,842,150
Share price (in dollars per share)	$ 28.50		$ 28.50
Underwriter's discount and offering expenses	$ 24,800,000
Net proceeds from sale of shares	$ 377,700,000	$ 0	$ 377,703,000
Preferred stock, authorized (in shares)		200,000,000
Preferred stock, par value (in dollars per share)		$ 0.01
Preferred stock, shares issued (in shares)		0
Preferred stock, shares outstanding (in shares)		0
Convertible debt securities
Class of Stock [Line Items]
Common stock shares reserved for issuance (in shares)		11,492,280
Aggregate principal amount		$ 450,000,000
Stock options to purchase common stock
Class of Stock [Line Items]
Common stock shares reserved for issuance (in shares)		9,608,344
Unvested RSUs
Class of Stock [Line Items]
Common stock shares reserved for issuance (in shares)		244,801
1.75 convertible senior notes due 2025 | Convertible debt securities
Class of Stock [Line Items]
Aggregate principal amount				$ 450,000,000
Convertible Notes ($450.0 face value)				309,100,000
Equity component of convertible debt				$ 140,900,000

Shareholders' Equity - Changes

Shareholders' Equity - Changes in Shareholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at December 31, 2017			$ 361,059
Net loss for the period	$ (87,743)	$ (45,179)	(232,704)	$ (127,265)
Proceeds from exercise of stock options			6,390
Equity component of Convertible Notes			136,434
Stock-based compensation expense			20,205
Change in cumulative translation adjustment	2	$ 76	23	$ 99
Balance at September 30, 2018	$ 291,407		$ 291,407

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions	May 15, 2018	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017	May 18, 2017
Stock-Based Compensation
Shares of common stock, maximum authorized for issuance (in shares)					5,000,000
Shares available for grant (in shares)		3,408,995	3,408,995
Inducement stock options granted to new employees (in shares)			236,730
Options outstanding (in shares)		9,608,344	9,608,344	8,608,921
Performance options
Stock-Based Compensation
Value of options vested		$ 1.1
Options vested (in shares)		133,334
Options outstanding (in shares)		0	0
2018 Employee Stock Purchase Plan
Stock-Based Compensation
Shares of common stock, maximum authorized for issuance (in shares)	1,000,000
Number of additional shares authorized (in shares)	1,200,000
Percentage of outstanding shares	2.00%

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Number of Shares
Options outstanding beginning of the period (in shares)			8,608,921
Granted (in shares)			1,610,010
Exercised (in shares)			(427,729)
Forfeited or expired (in shares)			(182,858)
Options outstanding end of the period (in shares)	9,608,344		9,608,344
Vested and expected to vest (in shares)	8,760,828		8,760,828
Exercisable (in shares)	5,317,732		5,317,732
Weighted Average Exercise Price
Options outstanding beginning of the period (in dollars per share)			$ 14.08
Granted (in dollars per share)			28.57
Exercised (in dollars per share)			14.94
Forfeited or expired (in dollars per share)			19.15
Options outstanding end of the period (in dollars per share)	$ 16.37		16.37
Vested and expected to vest (in dollars per share)	15.90		15.90
Exercisable (in dollars per share)	$ 13.23		$ 13.23
Weighted Average Remaining Contractual Life in Years
Options outstanding			7 years 29 days
Vested and expected to vest			6 years 11 months 1 day
Exercisable			5 years 11 months 15 days
Aggregate Intrinsic Value
Options outstanding	$ 52,765		$ 52,765
Vested and expected to vest	50,354		50,354
Exercisable	$ 38,723		$ 38,723
Stock options to purchase common stock
Fair value and assumptions used in determining fair value of stock options
Dividend yield	0.00%	0.00%	0.00%	0.00%
Expected option term (in years)	5 years 1 month 20 days	6 years 3 months	5 years 1 month 2 days	6 years 3 months
Weighted average fair value of stock options granted (in dollars per share)	$ 13.62	$ 9.59	$ 16.56	$ 10.18
Stock options to purchase common stock | Minimum
Fair value and assumptions used in determining fair value of stock options
Volatility	66.00%	72.00%	66.00%	72.00%
Risk-free interest rate	2.75%	1.73%	2.25%	1.73%
Stock options to purchase common stock | Maximum
Fair value and assumptions used in determining fair value of stock options
Volatility	67.00%	73.00%	68.00%	74.00%
Risk-free interest rate	2.87%	1.93%	2.87%	1.99%

Stock-Based Compensation - Rang

Stock-Based Compensation - Range of Exercise Prices (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock options to purchase common stock
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Total intrinsic value of stock options exercised during the period	$ 0.6	$ 1.4	$ 5.5	$ 3.5
Unrecognized compensation expense related to unvested stock options	$ 34.7		$ 34.7
Expected weighted average period for recognized and unrecognized compensation expense			2 years 6 months
$3.03 to $6.90
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			$ 3.03
Range of Exercise Prices upper range limit (in dollars per share)			$ 6.90
Number of Options Outstanding (in shares)	1,087,941		1,087,941
Weighted Average Remaining Contractual Term (in years)			3 years 11 months 8 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 3.99		$ 3.99
Number of Options Exercisable (in shares)	1,087,941		1,087,941
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 3.99		$ 3.99
$6.96 to $10.85
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			6.96
Range of Exercise Prices upper range limit (in dollars per share)			$ 10.85
Number of Options Outstanding (in shares)	997,221		997,221
Weighted Average Remaining Contractual Term (in years)			7 years 6 months 10 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 10.77		$ 10.77
Number of Options Exercisable (in shares)	481,574		481,574
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 10.68		$ 10.68
$11.14 to $12.58
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			11.14
Range of Exercise Prices upper range limit (in dollars per share)			$ 12.58
Number of Options Outstanding (in shares)	984,936		984,936
Weighted Average Remaining Contractual Term (in years)			5 years 5 months 26 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 12.17		$ 12.17
Number of Options Exercisable (in shares)	893,989		893,989
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 12.20		$ 12.20
$12.66 to $13.67
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			12.66
Range of Exercise Prices upper range limit (in dollars per share)			$ 13.67
Number of Options Outstanding (in shares)	984,161		984,161
Weighted Average Remaining Contractual Term (in years)			7 years 11 months 19 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 13.60		$ 13.60
Number of Options Exercisable (in shares)	428,577		428,577
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 13.56		$ 13.56
$13.94 to $16.07
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			13.94
Range of Exercise Prices upper range limit (in dollars per share)			$ 16.07
Number of Options Outstanding (in shares)	1,139,533		1,139,533
Weighted Average Remaining Contractual Term (in years)			6 years 9 months 18 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 15.26		$ 15.26
Number of Options Exercisable (in shares)	765,384		765,384
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 15.17		$ 15.17
$16.09 to $17.16
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			16.09
Range of Exercise Prices upper range limit (in dollars per share)			$ 17.16
Number of Options Outstanding (in shares)	1,438,502		1,438,502
Weighted Average Remaining Contractual Term (in years)			7 years 11 months 12 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 16.69		$ 16.69
Number of Options Exercisable (in shares)	602,949		602,949
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 16.48		$ 16.48
$17.24 to $22.76
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			17.24
Range of Exercise Prices upper range limit (in dollars per share)			$ 22.76
Number of Options Outstanding (in shares)	1,366,680		1,366,680
Weighted Average Remaining Contractual Term (in years)			6 years 6 months 21 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 21.20		$ 21.20
Number of Options Exercisable (in shares)	1,017,263		1,017,263
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 21.26		$ 21.26
$22.84 to $30.46
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			22.84
Range of Exercise Prices upper range limit (in dollars per share)			$ 30.46
Number of Options Outstanding (in shares)	1,439,910		1,439,910
Weighted Average Remaining Contractual Term (in years)			9 years 2 months 15 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 28.61		$ 28.61
Number of Options Exercisable (in shares)	40,055		40,055
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 24.26		$ 24.26
$30.86 to $31.78
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			30.86
Range of Exercise Prices upper range limit (in dollars per share)			$ 31.78
Number of Options Outstanding (in shares)	155,960		155,960
Weighted Average Remaining Contractual Term (in years)			9 years 3 months
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 31.10		$ 31.10
Number of Options Exercisable (in shares)	0		0
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 0		$ 0
$32.46 to $32.46
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range
Range of Exercise Prices lower range limit (in dollars per share)			32.46
Range of Exercise Prices upper range limit (in dollars per share)			$ 32.46
Number of Options Outstanding (in shares)	13,500		13,500
Weighted Average Remaining Contractual Term (in years)			9 years 3 months 3 days
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$ 32.46		$ 32.46
Number of Options Exercisable (in shares)	0		0
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$ 0		$ 0

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock and Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock options and RSUs
Weighted Average Grant Price
Allocated share-based compensation expense	$ 7.9	$ 4.7	$ 20.2	$ 13.3
Stock options and RSUs | Research and development expenses
Weighted Average Grant Price
Allocated share-based compensation expense	2.8	1.8	7.4	4.8
Stock options and RSUs | General and administrative expenses
Weighted Average Grant Price
Allocated share-based compensation expense	5.1	$ 2.9	$ 12.8	$ 8.5
RS and RSUs
Stock-Based Compensation
Number of common shares each award holder is entitled to receive			1
Unvested RSUs
Stock-Based Compensation
Unrecognized compensation expense	$ 4.2		$ 4.2
Expected weighted average period for recognized and unrecognized compensation expense			2 years 9 months 18 days
Number of RSUs
Outstanding, beginning balance (in shares)			46,914
Granted (in shares)			248,468
Released (in shares)			(47,478)
Forfeited (in shares)			(3,103)
Outstanding, ending balance (in shares)	244,801		244,801
Weighted Average Grant Price
Outstanding Weighted Average Grant Price (in dollars per share)			$ 17.16
Granted (in dollars per share)			29.41
Released (in dollars per share)			17.32
Forfeited (in dollars per share)			30.46
Outstanding Weighted Average Grant Price (in dollars per share)	$ 29.40		$ 29.40

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 46,000	$ 27,000	$ 134,000	$ 94,000
Deferred tax benefit			0
Provisional deferred tax asset offset completely by valuation allowance					$ 94,000,000
Unrecognized income tax benefits, interest and penalties accrued	$ 0		$ 0		$ 0

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)renewal	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)
Commitments
Future minimum rental payments under lease	$ 37,038	$ 37,038		$ 37,038
Rent expense charged to operations		400	$ 400	1,200	$ 1,100
Bridgewater, NJ facility
Commitments
Future minimum rental payments under lease	1,200	1,200		1,200
Future minimum rental payments for additional laboratory space	1,500	1,500		1,500
Bridgewater, NJ office space
Commitments
Future minimum rental payments under lease	$ 32,300	$ 32,300		$ 32,300
Initial lease term	130 months
Option to extend lease term | renewal	3
Period of lease extension	5 years

Commitments and Contingencies_2

Commitments and Contingencies - Minimum Rental Payments (Details) $ in Thousands	Sep. 30, 2018USD ($)
Future minimum rental payments under operating leases
2018 (remaining)	$ 490
2,019	3,863
2,020	4,185
2,021	3,958
2,022	1,281
2023 and thereafter	23,261
Total	$ 37,038