Insmed (INSM) 10-K 6 Mar 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Feb. 27, 2014	Jun. 30, 2013
Document and Entity Information	'	'	'
Entity Registrant Name	'INSMED INC	'	'
Entity Central Index Key	'0001104506	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
Amendment Flag	'false	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'No	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Filer Category	'Accelerated Filer	'	'
Entity Public Float	'	'	$345.20
Entity Common Stock, Shares Outstanding	'	39,263,837	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$113,894	$90,782
Certificate of deposit	'	2,153
Prepaid expenses and other current assets	2,269	643
Total current assets	116,163	93,578
In-process research and development	58,200	58,200
Other assets	323	117
Fixed assets, net	1,812	1,666
Total assets	176,498	153,561
Current liabilities:	'	'
Accounts payable	5,929	7,060
Accrued expenses	3,905	2,933
Accrued compensation	2,839	2,207
Accrued lease expense, current	307	295
Deferred rent	129	149
Capital lease obligations, current	64	96
Current portion of long term debt	3,283	3,007
Total current liabilities	16,456	15,747
Accrued lease expense, long-term	380	647
Capital lease obligations, long-term	'	64
Debt, long-term	16,338	16,221
Total liabilities	33,174	32,679
Shareholders' equity:	'	'
Common stock, $0.01 par value; 500,000,000 authorized shares, 39,137,679 and 31,488,204 issued and outstanding shares at December 31, 2013 and December 31, 2012, respectively.	391	315
Additional paid-in capital	534,554	455,325
Warrant to purchase common stock	'	790
Accumulated deficit	-391,621	-335,548
Total shareholders' equity	143,324	120,882
Total liabilities and shareholders' equity	$176,498	$153,561

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Consolidated Balance Sheets	'	'
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, authorized shares	500,000,000	500,000,000
Common stock, issued shares	39,137,679	31,488,204
Common stock, outstanding shares	39,137,679	31,488,204

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements of Comprehensive Loss	'	'	'
License fees	'	'	$1,002
Other revenue	11,500	'	'
Other expanded access program income, net	'	'	3,415
Total revenues	11,500	'	4,417
Operating expenses:	'	'	'
Research and development	44,279	29,781	28,623
General and administrative	22,236	12,657	11,523
Impairment loss	'	'	25,990
Total operating expenses	66,515	42,438	66,136
Operating loss	-55,015	-42,438	-61,719
Investment income	166	1,822	2,064
Interest expense	-2,412	-763	-10
Other, net	-33	5	1
Loss before income taxes	-57,294	-41,374	-59,664
Benefit from income taxes	-1,221	0	0
Net loss	-56,073	-41,374	-59,664
Accretion of beneficial conversion charge	'	'	-9,175
Net loss attributable to common stockholders	-56,073	-41,374	-68,839
Basic and diluted net loss attributable to common stockholders per share (in dollars per share)	($1.60)	($1.56)	($2.95)
Weighted average basic and diluted common shares outstanding (in shares)	34,980	26,545	23,348
Net loss attributable to common stockholders	-56,073	-41,374	-68,839
Comprehensive loss:	'	'	'
Unrealized loss on investments	'	-450	-543
Comprehensive loss attributable to common stockholders	($56,073)	($41,824)	($69,382)

Consolidated_Statements_of_Sto

Consolidated Statements of Stockholders' Equity (USD $)	Total	Common Stock	Preferred Stock	Warrant	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
In Thousands, except Share data, unless otherwise specified
Balance at Dec. 31, 2010	$192,843	$1,565	$918	'	$423,877	($234,510)	$993
Balance (in shares) at Dec. 31, 2010	'	15,654,000	9,175,000	'	'	'	'
Comprehensive loss:	'	'	'	'	'	'	'
Net loss	-59,664	'	'	'	'	-59,664	'
Unrealized loss on investments	-543	'	'	'	'	'	-543
1 for 10 reverse stock split	'	-2,235	'	'	2,235	'	'
Exercise of stock options	32	'	'	'	32	'	'
Exercise of stock options (in shares)	5,200	5,000	'	'	'	'	'
Conversion of preferred stock into common stock	'	918	-918	'	'	'	'
Conversion of preferred stock into common stock (in shares)	'	9,174,000	-9,175,000	'	'	'	'
Stock compensation expense	1,599	'	'	'	1,599	'	'
Balance at Dec. 31, 2011	134,267	248	'	'	427,743	-294,174	450
Balance (in shares) at Dec. 31, 2011	'	24,833,000	'	'	'	'	'
Comprehensive loss:	'	'	'	'	'	'	'
Net loss	-41,374	'	'	'	'	-41,374	'
Unrealized loss on investments	-450	'	'	'	'	'	-450
Exercise of stock options	214	1	'	'	213	'	'
Exercise of stock options (in shares)	30,250	30,000	'	'	'	'	'
Net proceeds from the issuance of common stock	25,658	63	'	'	25,595	'	'
Net proceeds from the issuance of common stock (in shares)	'	6,304,000	'	'	'	'	'
Issuance of common stock for vesting of RSUs	'	3	'	'	-3	'	'
Issuance of common stock for vesting of RSUs (in shares)	'	321,000	'	'	'	'	'
Fair value of warrants granted in connection with debt financing	790	'	'	790	'	'	'
Fair value of warrants granted in connection with debt financing (in shares)	'	'	'	330,000	'	'	'
Stock compensation expense	1,777	'	'	'	1,777	'	'
Balance at Dec. 31, 2012	120,882	315	'	790	455,325	-335,548	'
Balance (in shares) at Dec. 31, 2012	'	31,488,000	'	330,000	'	'	'
Comprehensive loss:	'	'	'	'	'	'	'
Net loss	-56,073	'	'	'	'	-56,073	'
Exercise of stock options	1,626	4	'	'	1,622	'	'
Exercise of stock options (in shares)	371,743	372,000	'	'	'	'	'
Net proceeds from the issuance of common stock	67,017	69	'	'	66,948	'	'
Net proceeds from the issuance of common stock (in shares)	'	6,900,000	'	'	'	'	'
Issuance of common stock for vesting of RSUs	'	1	'	'	-1	'	'
Issuance of common stock for vesting of RSUs (in shares)	'	154,000	'	'	'	'	'
Exercise of warrants	'	2	'	-790	788	'	'
Exercise of warrants (in shares)	'	223,000	'	-330,000	'	'	'
Reclass of stock compensation expense for liability awards to equity	3,371	'	'	'	3,371	'	'
Stock compensation expense	6,501	'	'	'	6,501	'	'
Balance at Dec. 31, 2013	$143,324	$391	'	'	$534,554	($391,621)	'
Balance (in shares) at Dec. 31, 2013	'	39,137,000	'	'	'	'	'

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities	'	'	'
Net loss	($56,073)	($41,374)	($59,664)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'
Depreciation and amortization	680	561	343
Stock based compensation expense	8,668	2,981	1,599
Gain on sale of asset, net	-2	-5	-1
Gain on sale of short-term investments, net	'	-833	'
Impairment loss	'	'	25,990
Amortization of debt discount and debt issuance costs	333	236	'
Accrual of the end of term charge on the debt	160	44	'
Changes in operating assets and liabilities:	'	'	'
Accounts receivable	'	757	-286
Prepaid expenses and other assets	-1,832	-180	-214
Accounts payable	-1,131	4,726	884
Accrued expenses and deferred rent	2,156	922	667
Accrued lease expenses	-255	-259	1,201
Accrued compensation	632	1,412	-322
Deferred revenue	'	'	-402
Net cash used in operating activities	-46,664	-31,012	-30,205
Investing activities	'	'	'
Purchase of fixed assets	-826	-290	-979
Proceeds from sale of asset	2	5	'
Maturity of a certificate of deposit	2,153	'	'
Sales of short-term investments	'	81,464	36,500
Purchases of short-term investments	'	-19,657	-1,161
Net cash provided by investing activities	1,329	61,522	34,360
Financing activities	'	'	'
Payments on capital lease obligations	-96	-120	-82
Proceeds from issuance of debt	'	20,000	'
Proceeds from issuance of common stock	67,017	25,658	'
Proceeds from exercise of stock options	1,626	214	32
Payment of debt issuance costs	-100	-328	'
Net cash provided by (used in) financing activities	68,447	45,424	-50
Increase in cash and cash equivalents	23,112	75,934	4,105
Cash and cash equivalents at beginning of period	90,782	14,848	10,743
Cash and cash equivalents at end of period	113,894	90,782	14,848
Supplemental disclosures of cash flow information:	'	'	'
Cash paid for interest	1,809	398	10
Cash received for taxes, net	1,221	'	'
Supplemental disclosures of non-cash investing and financing activities:	'	'	'
Capital lease obligations incurred	'	'	198
Unrealized loss on investments	'	-450	-543
Accretion of beneficial conversion charge	'	'	-9,175
Value of warrant exercised by converting the warrant into shares of common stock ("net issuance method")	790	'	'
Fair value of warrant granted in connection with debt financing	'	790	'
Conversion of Series B preferred stock into common stock	'	'	$918

Description_of_Business_and_Ba

Description of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2013
Description of Business and Basis of Presentation	'
Description of Business and Basis of Presentation	'
	1.        Description of Business and Basis of Presentation
	Description of Business—Insmed is a biopharmaceutical company focused on developing and commercializing inhaled therapies for patients battling serious lung diseases that are often life threatening. The Company's lead product candidate, ARIKAYCE®, or liposomal amikacin for inhalation, is an inhaled antibiotic treatment that delivers a proven and potent anti-infective directly to the site of serious lung infections.
	The Company is currently conducting a phase 2 clinical trial in the United States (US) and Canada of ARIKAYCE in patients who have lung infections caused by non-tuberculous mycobacteria (NTM) and the Company expects to report top-line clinical results from the double-blind phase of this clinical trial in March 2014. In 2013, the Company concluded a phase 3 clinical trial in Europe and Canada of ARIKAYCE in cystic fibrosis (CF) patients who have lung infections caused by Pseudomonas aeruginosa (Pseudomonas). The CF and NTM target indications address orphan patient populations. The Company's strategy includes plans to continue to develop ARIKAYCE to broaden the NTM indication and for additional indications beyond Pseudomonas in CF and NTM. The Company also plans to develop, acquire, in-license or co-promote other products that address orphan or rare diseases in the fields of pulmonology and infectious disease. The Company's current primary development focus is to obtain regulatory approval for ARIKAYCE in these two initial indications and to prepare for commercialization in the United States, Europe, Japan and Canada. If approved, ARIKAYCE will be the first once-a-day inhaled antibiotic treatment option available for these CF and NTM indications.
	The Company was incorporated in the Commonwealth of Virginia on November 29, 1999. On December 1, 2010, the Company completed a business combination with Transave, Inc. (Transave), a privately held, New Jersey-based pharmaceutical company focused on the development of differentiated and innovative inhaled pharmaceuticals for the treatment of serious lung infections. The integration with Transave was completed in 2011. The Company's continuing operations are based on the technology and products historically developed by Transave. The Company's principal executive offices are located in Monmouth Junction, New Jersey.
	Basis of Presentation—The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Transave, LLC, Insmed Pharmaceuticals, Incorporated, Insmed Limited, and Celtrix Pharmaceuticals, Incorporated (Celtrix). All significant intercompany balances and transactions have been eliminated in consolidation.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Summary of Significant Accounting Policies	'
	2.        Summary of Significant Accounting Policies
	Use of Estimates—The preparation of the consolidated financial statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. The Company bases its estimates and judgments on historical experience and on various other assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company's balance sheets and the amounts of revenue and expenses reported for each period presented are effected by estimates and assumptions, which are used for, but not limited to, the accounting for revenue recognition, stock-based compensation, income taxes, loss contingencies, the beneficial conversion charge, the warrant fair value calculation, impairment of intangibles and long lived assets and accounting for research and development costs. Actual results could differ from those estimates.
	Prior Period Reclassifications—Certain amounts in the 2011 consolidated financial statements were reclassified to conform to the 2012 presentation. Specifically, the Company allocated a portion of certain operating expenses from general and administrative expense to research and development expense in 2012 and recast the 2011 amounts to conform to the current year presentation for comparability purposes.
	Investment Income and Interest Expense—Investment income consists of interest and dividend income earned on our cash, cash equivalents and short-term investments, along with realized gains (losses) on the sale of investments. Interest expense consists primarily of interest costs related to our debt and capital lease obligations.
	Cash and Cash Equivalents—The Company considers cash equivalents to be highly liquid investments with maturities of three months or less from the date of purchase.
	Fixed Assets, Net—Fixed assets are recorded at cost and are depreciated on a straight-line basis over the estimated useful lives of the assets. Estimated useful lives of three to seven years are used for computer equipment, laboratory equipment, office equipment and furniture and fixtures. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset. Long-lived assets, such as lab equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, then an impairment charge is recognized for the amount by which the carrying value of the asset exceeds the fair value of the asset.
	Identifiable Intangible Assets—Identifiable intangible assets are measured at their respective fair values and are not amortized until commercialization. Once commercialization occurs, these intangible assets will be amortized over their estimated useful lives. The fair values assigned to the Company's intangible assets are based on reasonable estimates and assumptions given available facts and circumstances. Unanticipated events or circumstances may occur that may require the Company to review the assets for impairment. Events or circumstances that may require an impairment assessment include negative clinical trial results, the non-approval of a new drug application by a regulatory agency, material delays in our development program or a sustained decline in market capitalization.
	Indefinite-lived intangible assets are not subject to periodic amortization. Rather, indefinite-lived intangibles are reviewed for impairment by applying a fair value based test on an annual basis or more frequently if events or circumstances indicate impairment may have occurred. Events or circumstances that may require an interim impairment assessment are consistent with those described above. The Company performs its annual impairment test as of October 1 of each year.
	The Company uses the income approach to derive the fair value of in-process research and development assets. This approach calculates fair value by estimating future cash flows attributable to the assets and then discounting these cash flows to a present value using a risk-adjusted discount rate. A market based valuation approach was not considered given a lack of revenues and profits for the Company. This approach requires significant management judgment with respect to unobservable inputs such as future volume, revenue and expense growth rates, changes in working capital use, appropriate discount rates and other assumptions and estimates. The estimates and assumptions used are consistent with the Company's business plans.
	Debt Issuance Costs—Debt issuance costs are amortized using the effective interest rate method, and amortized to interest expense over the term of the debt. Debt issuance costs paid to the lender are reflected as a discount to the debt, and debt issuance costs paid to other third parties are reflected as other assets in the consolidated balance sheets.
	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 judgments 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 are categorized in the tables below 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 following table presents assets and liabilities measured at fair value as of December 31, 2013 and December 31, 2012 (in thousands).
		Fair Value Measurements at Reporting Date Using
		Total			Quoted Prices in			Quoted Prices in			Significant
					Active Markets for			Inactive Markets for			Unobservable Inputs
					Identical Assets			Identical Assets			(Level 3)
					(Level 1)			(Level 2)
	As of December 31, 2013:
	Assets:
	Cash and cash equivalents	$	113,894		$	113,894		$	-		$	-
		$	113,894		$	113,894		$	-		$	-
	As of December 31, 2012:
	Assets:
	Cash and cash equivalents	$	90,782		$	90,782		$	-		$	-
	Certificate of deposit		2,153			2,153			-			-
		$	92,935		$	92,935		$	-		$	-
	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 a maturity of three months or less from the date of purchase and the short-term investments consist of instruments with maturities greater than three months.
	We recognize 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 2013 and 2012.
	As of December 31, 2013 and 2012, the Company held no securities that were in an unrealized loss or gain position. The Company's unrealized loss on investments for the years ended 2012 and 2011 of $0.5 million and $0.5 million, respectively, previously were presented incorrectly as zero and a gain of $0.5 million, respectively, in the prior year's Consolidated Statements of Comprehensive Loss. The Company's comprehensive loss is now correctly presented. There was no impact on net loss during either period as a result of the correction of these immaterial clerical errors. During 2012, the Company realized a net gain of $0.8 million from the sale of short term investments.
	The Company reviews the status of each security quarterly to determine whether an other-than-temporary impairment has occurred. In making our determination, we consider 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) our ability and intent to retain the investment for a sufficient period of time for it to recover.
	Concentration of Credit Risk—Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents and short-term investments. The Company places its cash equivalents with high credit-quality financial institutions and may invest its short-term investments in US treasury securities, mutual funds and government agency bonds. The Company has established guidelines relative to credit ratings and maturities that seek to maintain safety and liquidity.
	The Company sources its raw materials from single suppliers. In addition, the production of the Company's product candidate is performed by a sole manufacturer. The inability of the suppliers or manufacturer to fulfill supply requirements of the Company could materially impact future operating results. A change in the relationship with the suppliers or manufacturer, or an adverse change in their business, could materially impact future operating results.
	Revenue Recognition—In 2013, the Company's other revenue solely consists of an $11.5 million payment received from Premacure (now Shire plc) in exchange for the Company's right to receive royalties under its license agreement with Premacure. We recorded this as other revenue after all four revenue recognition criteria were present and the Company had no continuing performance obligations related to the payment received. The Company's revenues in 2011 were from (1) $3.4 million of cost recovery revenues from the use of IPLEX® in an Expanded Access Program (EAP) the Company established in Italy to provide IPLEX® to physicians for use in their patients with Amyotrophic Lateral Sclerosis (ALS) (this program was discontinued in December 2011), and (2) a $1.0 million non-refundable upfront license payment received from Eleison Pharmaceuticals, Inc. (Eleison") for the licensing of the Company's lipid-complexed cisplatin and/or liposomal cisplatin products and technology to Eleison. We recorded this revenue during 2011 as we had the contractual right to receive it and we have no continuing involvement under this licensing agreement.
	The Company recognizes revenues when all of the following four criteria are present: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the fee is fixed or determinable; and collectability is reasonably assured.
	Where the Company has continuing performance obligations under the terms of a collaborative arrangement, non-refundable upfront license payments received upon contract signing are recorded as deferred revenue and recognized as revenue as the related activities are performed. The period over which these activities are to be performed is based upon management's estimate of the development period. Changes in management's estimate could change the period over which revenue is recognized. Research and/or development payments are recognized as revenues as the related research and/or development activities are performed and when the Company has no continuing performance obligations related to the research and development payment received.
	Where the Company has no continuing involvement under a collaborative arrangement, the Company records nonrefundable license fee revenues when the Company has the contractual right to receive the payment, in accordance with the terms of the collaboration agreement, and records milestones upon appropriate notification to the Company of achievement of the milestones by the collaborative partner.
	The Company recognizes revenue from milestone payments when earned, provided that (i) the milestone event is substantive and its achievability was not reasonably assured at the inception of the agreement and (ii) the Company does not have ongoing performance obligations related to the achievement of the milestone earned. Milestone payments are considered substantive if all of the following conditions are met: the milestone payment (a) is commensurate with either the vendor's performance to achieve the milestone or the enhancement of the value of the delivered item or items as a result of a specific outcome resulting from the vendor's performance to achieve the milestone, (b) relates solely to past performance, and (c) is reasonable relative to all of the deliverables and payment terms (including other potential milestone consideration) within the arrangement. Any amounts received under the agreement in advance of performance, if deemed substantive, are recorded as deferred revenue and recognized as revenue as the Company completes its performance obligations.
	With regard to recognizing revenue for multiple deliverable revenue arrangements, each deliverable within a multiple-deliverable revenue arrangement is accounted for as a separate unit of accounting if both of the following criteria are met: (1) the delivered item or items have value to the customer on a standalone basis and (2) for an arrangement that includes a general right of return relative to the delivered item(s), delivery or performance of the undelivered item(s) is considered probable and substantially in our control.
	In addition, multiple deliverable revenue arrangement consideration is allocated at the inception of an arrangement to all deliverables using the relative selling price method. The Company also applies a selling price hierarchy for determining the selling price of a deliverable, which includes (1) vendor-specific objective evidence, if available, (2) third-party evidence, if vendor-specific objective evidence is not available, and (3) estimated selling price if neither vendor-specific nor third-party evidence is available.
	Deferred revenue associated with a non-refundable payment received under a collaborative agreement that is terminated prior to its completion results in an immediate recognition of the deferred revenue.
	Research and Development—Research and development expenses consist primarily of salaries, benefits and other related costs, including stock based compensation, for personnel serving in our research and development functions, and other internal operating expenses, the cost of manufacturing our drug candidate, including the medical devices for drug delivery, for clinical study, the cost of conducting clinical studies, and the cost of conducting preclinical and research activities. The Company's expenses related to manufacturing its drug candidate and medical devices for clinical study are primarily related to activities at contract manufacturing organizations that manufacture ARIKAYCE and the medical devices for the Company's use. The Company's expenses related to clinical trials are primarily related to activities at contract research organizations that conduct and manage clinical trials on the Company's behalf. These contracts set forth the scope of work to be completed at a fixed fee or amount per patient enrolled. Payments under these contracts primarily depend on performance criteria such as the successful enrollment of patients or the completion of clinical trial milestones as well as time-based fees. Expenses are accrued based on contracted amounts applied to the level of patient enrollment and to activity according to the clinical trial protocol. Nonrefundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized. Such amounts are then recognized as an expense as the related goods are delivered or the services are performed, or when the goods or services are no longer expected to be provided.
	Stock-Based Compensation—The Company recognizes stock-based compensation expense for awards of equity instruments to employees and directors based on the grant-date fair value of those awards. The grant-date fair value of the award is recognized as compensation expense ratably over the requisite service period, which generally equals the vesting period of the award, and if applicable, is adjusted for expected forfeitures. We also grant performance-based stock options to employees. The grant-date fair value of the performance-based stock options is recognized as compensation expense over the implicit service period using the accelerated attribution method once it is probable that the performance condition will be achieved. Stock-based compensation expense is included in both research and development expenses and general and administrative expenses in the Consolidated Statements of Comprehensive Loss.
	Certain awards deemed to be granted outside of the Company's equity incentive plans require the Company to use liability accounting. These awards are classified as a liability and are remeasured at fair value at the end of each reporting period until such time they are deemed to be granted under the Company's equity incentive plans. Changes in fair value are included in compensation expense in the Consolidated Statements of Comprehensive Loss (see additional disclosures related to awards granted outside of the 2000 Stock Incentive Plan in Footnote 9, Stock-Based Compensation).
	Income Taxes—The Company accounts for income taxes under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date.
	A valuation allowance is recorded to reduce the deferred tax assets to the amount that is expected to be realized. In evaluating the need for a valuation allowance, we take into account various factors, including the expected level of future taxable income and available tax planning strategies. If actual results differ from the assumptions made in the evaluation of our valuation allowance, we record a change in valuation allowance through income tax expense in the period such determination is made.
	The Company uses a comprehensive model for how it measures, presents and discloses an uncertain tax position taken or expected to be taken in a tax return. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by taxing authorities, based solely on the technical merits of the position. The tax benefits recognized in the financial statements from such a position should be measured based on the largest benefit that has a greater than 50% likelihood to be sustained upon ultimate settlement. The Company has no uncertain tax positions as of December 31, 2013 that qualify for either recognition or disclosure in the consolidated financial statements.
	The Company's policy for interest and penalties related to income tax exposures is to recognize interest and penalties as a component of the income taxes on continuing operations in the Consolidated Statements of Comprehensive Loss.
	Net Loss Per Common Share—Basic net loss per common share is computed by dividing net loss attributable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted net loss per common share is computed by dividing net loss attributable to common stockholders 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 and warrants to purchase common stock would be antidilutive as the Company incurred a net loss. Potentially dilutive common shares resulting from the assumed exercise of outstanding stock options and warrants are determined based on the treasury stock method.
	The following table sets forth the reconciliation of the weighted average number of shares attributable to common stockholders used to compute basic net loss per share for the years ended December 31, 2013, 2012 and 2011.
		Twelve Months Ended December 31,
		2013			2012			2011
		(In thousands, except per share amounts)
	Numerator:
	Net loss attributable to common stockholders:	$	(56,073	)	$	(41,374	)	$	(68,839	)
	Denominator:
	Weighted average common shares used in calculation of basic net loss per share:		34,980			26,545			23,348
Effect of dilutive securities:
Common stock options		-			-			-
Restricted stock and restricted stock units		-			-			-
Common stock warrant		-			-			-
Weighted average common shares outstanding used in calculation of diluted net loss per share		34,980			26,545			23,348
Net loss per share:
Basic and Diluted	$	(1.60	)	$	(1.56	)	$	(2.95	)
The following potentially dilutive securities have been excluded from the computations of diluted weighted-average common shares outstanding as of December 31, 2013, 2012 and 2011 as their effect would have been anti-dilutive (in thousands).
	2013			2012			2011
Warrants to purchase common stock		-			330			158
Stock options to purchase common stock		3,633			1,818			892
Restricted stock and restricted stock units		93			216			487
Segment Information—The Company currently operates in one business segment, which is the development and commercialization of inhaled therapies for patients with serious lung diseases. A single management team that reports to the Chief Executive Officer comprehensively manages the entire business. The Company does not operate separate lines of business with respect to its products or product candidates. Accordingly, the Company does not have separate reportable segments.
Recently Adopted Accounting Pronouncements—In February 2013, an Accounting Standards Update was issued that requires companies to present either in a single note or parenthetically on the face of the financial statements, the effect of significant amounts reclassified from each component of accumulated other comprehensive income (loss) based on its source and the income statement line items affected by the reclassification. This guidance is effective for annual and interim reporting periods beginning after December 15, 2012. This became effective for the Company on January 1, 2013 and its adoption did not impact the Company's consolidated financial statements.
In July 2012, an Accounting Standards Update was issued that allows companies to assess qualitative factors to determine the likelihood of indefinite-lived intangible asset impairment and whether it is necessary to perform the quantitative impairment test currently required. This guidance is effective for annual and interim impairment tests performed for fiscal years beginning after September 15, 2012, with early adoption permitted. This became effective for us on January 1, 2013 and its adoption did not impact the Company's consolidated financial statements.
In December 2011, an Accounting Standards Update was issued that requires disclosure of information about offsetting assets and liabilities and related arrangements to enable users of the Company's consolidated financial statements to understand the effect of those arrangements on the Company's financial position. The new guidance is effective for annual reporting periods beginning on or after January 1, 2013, and interim periods within those annual periods. This became effective for the Company on January 1, 2013 and its adoption did not impact the Company's consolidated financial statements.

Beneficial_Conversion_Charge_B

Beneficial Conversion Charge ("BCC")	12 Months Ended
	Dec. 31, 2013
Beneficial Conversion Charge ("BCC")	'
Beneficial Conversion Charge ("BCC")	'
	3.        Beneficial Conversion Charge ("BCC")
	When issuing debt or equity securities that are convertible into common stock at a discount from the fair value of the common stock at the date the debt or equity financing is committed, the Company is required to record a BCC in accordance with Accounting Standards Codification ("ASC") 470-20. This BCC is measured as the difference between the fair values of the securities at the time of issue and the fair value of the common stock at the commitment date.
	In 2011, a non-cash BCC of $9.2 million was recorded when the Series B Preferred Stock was converted into common stock. The BCC represents a $1.00 per share discount on the fair value of our common stock. The carrying value of the preferred stock was based on its fair value at issuance, which was estimated using the common stock price reduced for a lack of marketability between the issuance date and the anticipated date of conversion.

Accrued_Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2013
Accrued Expenses	'
Accrued Expenses	'
	4.        Accrued Expenses
	Accrued expenses consist of the following:
		As of December 31,
		2013		2012
		(in thousands)
	Accrued clinical trial expenses	$	2,484	$	1,460
	Accrued technical operation expenses		1,220		-
	Liability for stock-based compensation awards		-		1,204
	Accrued professional fees		24		185
	Accrued interest payable		159		80
	Other accrued expenses		18		4
		$	3,905	$	2,933

Identifiable_Intangible_Assets

Identifiable Intangible Assets and Goodwill	12 Months Ended
	Dec. 31, 2013
Identifiable Intangible Assets and Goodwill	'
Identifiable Intangible Assets and Goodwill	'
	5.        Identifiable Intangible Assets and Goodwill
	In 2011, the Company recorded a non-cash impairment loss of $26.0 million related to the impairment of in-process research and development and goodwill. The impairment resulted from the fact that in August 2011, subsequent to our phase 2 trials and prior to starting a phase 3 trial, the Company announced that the FDA placed a clinical hold on its phase 3 clinical trials for ARIKAYCE in CF patients with Pseudomonas lung infections and in patients with NTM lung infections. A clinical hold is a notification issued by the FDA to the sponsor to delay a proposed clinical trial or suspend an ongoing clinical trial. The clinical holds were subsequently lifted in the first half of 2012.
	The Company's management determined the clinical hold was an indicator of possible impairment of in-process research and development and goodwill assets due to the associated additional costs, and, therefore, interim impairment testing was performed as of September 30, 2011. Using the income approach the impairment analysis compared the fair value of the in-process research and development intangible assets with their respective carrying amounts. This approach calculates fair value by estimating future cash flows attributable to the assets and then discounting these cash flows to a present value using a risk-adjusted discount rate. A market based valuation approach was not considered given a lack of revenues and profits for the Company. This approach requires significant management judgment with respect to unobservable inputs such as future volume, revenue and expense growth rates, changes in working capital use, appropriate discount rates and other assumptions and estimates. The estimates and assumptions used are consistent with the Company's business plans. Additionally, the carrying value of the business exceeded its fair value, and accordingly we performed the second step of the impairment test by comparing the carrying value of goodwill to its implied fair value. The impairment review resulted in impairment losses for both assets. Non-cash charges of $19.7 million and $6.3 million were recognized for the decline in the fair value of in-process research and development and goodwill assets, respectively, as of September 30, 2011. The non-cash charge of $26.0 million was recorded as an impairment loss and classified as an operating expense in the Consolidated Statements of Comprehensive Loss.
	We believe there are no indicators of impairment of the Company's in-process research and development intangible assets as of December 31, 2013.

Fixed_Assets_net

Fixed Assets, net	12 Months Ended
	Dec. 31, 2013
Fixed Assets, net	'
Fixed Assets, net	'
	6.        Fixed Assets, net
	Fixed assets are stated at cost and depreciated or amortized using the straight-line method, based on useful lives as follows:
			As of December 31,
		Estimated
	Asset Description	Useful Life (years)	2013			2012
			(in thousands)
	Lab equipment	7	$	3,371		$	2,872
	Furniture and fixtures	7		65			65
	Computer hardware and software	3 - 5		718			588
	Office equipment	7		117			117
	Manufacturing Equipment	7		375			325
	Leasehold improvements	lease term		612			581
	Construction in Progress (CIP)			116			-
				5,374			4,548
	Less accumulated depreciation and amortization			(3,562	)		(2,882	)
	Fixed assets, net		$	1,812		$	1,666
	Depreciation and amortization expense was $0.7 million, $0.6 million and $0.3 million for the years ended December 31, 2013, 2012 and 2011, respectively. Depreciation expense includes depreciation for equipment under capital lease obligations.
	Fixed assets include equipment held under capital lease obligations with an approximate net carrying value of $0.1 million and $0.3 million as of December 31, 2013 and 2012, respectively.

Debt

Debt	12 Months Ended
	Dec. 31, 2013
Debt	'
Debt	'
	7.        Debt
	On June 29, 2012, the Company and its domestic subsidiaries, as co-borrowers, entered into a Loan and Security Agreement that allowed the Company to borrow up $20.0 million in $10.0 million increments ("Loan Agreement"). The Company borrowed the first and second $10.0 million increments by signing two Secured Promissory Notes ("Note A" and "Note B" and collectively, the "Notes") on June 29, 2012 and December 27, 2012, respectively. Notes A and B bear interest at 9.25%. Note A was originally scheduled to be repaid over a 42-month period with the first twelve monthly payments representing interest only followed by thirty monthly equal payments of principal and interest. Note B was originally scheduled to be repaid over a 36-month period with the first six monthly payments representing interest only followed by thirty monthly equal payments of principal and interest. The Loan Agreement provided that in certain circumstances the Company could delay the first principal payment by five months. In July 2013, subsequent to the completion of certain ARIKAYCE-related development milestones, the Company elected to extend the interest only period under the Notes from July 31, 2013 to December 31, 2013 and delay the first monthly principal repayments for Notes A and B from August 1, 2013 to January 1, 2014. On November 25, 2013, the Company and Hercules entered into an amendment (the "Amendment") of the Loan Agreement. Pursuant to the Amendment, the interest-only period has been extended through June 30, 2014 and the first monthly principal payment is scheduled for July 1, 2014. The Amendment also allows the Company to further extend the interest-only period through December 31, 2014 and delay the first payment of principal until January 1, 2015, so long as the Company pays a $100,000 fee and obtains positive data from its phase 2 clinical trial of ARIKAYCE in patients who have lung infections caused by NTM. The election and amendment did not change the maturity date for Notes A and B, which is January 1, 2016.
	In connection with the Loan Agreement, the Company granted the lender a first position lien on all of the Company's assets, excluding intellectual property. Prepayment of the loans made pursuant to the Loan Agreement is subject to penalty and the Company is required to pay an "end of term" charge of $390,000, which is being charged to interest expense (and accreted to the debt) using the effective interest method over the life of the Loan Agreement. Debt issuance fees paid to the lender were recorded as a discount on the debt and are being amortized to interest expense using the effective interest method over the life of the Loan Agreement. Debt issuance fees paid to third parties were capitalized and are being amortized to interest expense using the effective interest method over the life of the Loan Agreement.
	The Loan Agreement also contains representations and warranties by us and the lender and indemnification provisions in favor of the lender and customary covenants (including limitations on other indebtedness, liens, acquisitions, investments and dividends, but no financial covenants), and events of default (including payment defaults, breaches of covenants following any applicable cure period, a material impairment in the perfection or priority of the lender's security interest or in the collateral, and events relating to bankruptcy or insolvency). Upon the occurrence of an event of default, a default interest rate of an additional 5% may be applied to the outstanding loan balances, and the lender may terminate its lending commitment, declare all outstanding obligations immediately due and payable, and take such other actions as set forth in the Loan Agreement. In addition, pursuant to the Loan Agreement, the lender has the right to participate, in an amount of up to $1.0 million, in certain future private equity financing(s) by the Company.
	In conjunction with entering into the Loan Agreement, the Company granted a warrant to the lender to purchase shares of the Company's common stock. Since the warrant was granted in conjunction with entering into the Loan Agreement, the relative fair value of the warrant was recorded as equity and debt discount. The debt discount is being amortized to interest expense over the term of the related debt using the effective interest method.
	The following table presents the components of the Company's debt balance as of December 31, 2013.
		December 31, 2013
		(in thousands)
	Debt:
	Notes payable	$	20,000
	Accretion of end of term charge		204
	Issuance fees paid to lender		(215	)
	Discount from warrant		(368	)
	Current portion of long-term debt		(3,283	)
	Long-term debt	$	16,338
	Future principal repayments of the two Notes are as follows (in thousands):
	Year Ending in December 31:
	2014	$	3,626
	2015		7,785
	2016		8,589
		$	20,000
	The estimated fair value of the debt (categorized as a Level 2 liability for fair value measurement purposes) is determined using current market factors and the ability of the Company to obtain debt at comparable terms to those that are currently in place. We believe the estimated fair value at December 31, 2013 approximates the carrying amount.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2013
Stockholders' Equity	'
Stockholders' Equity	'
	8.        Stockholders' Equity
	Common Stock—As of December 31, 2013, the Company had 500,000,000 shares of common stock authorized with a par value of $0.01 and 39,137,679 shares of common stock issued and outstanding. Of the shares outstanding as of December 31, 2013, 1,765,271 shares represent holdback shares held by the Company as security for potential indemnification payments, as described in the Agreement and Plan of Merger with Transave, Inc. (the "Merger Agreement"), filed as Exhibit 2.1 to the Company's Annual Report on Form 10-K for the year ended December 31, 2012 (see Footnote 12, Commitments and Contingencies, Legal Proceedings, Pilkiewicz v. Transave LLC for additional information regarding these holdback shares). In addition, as of December 31, 2013, the Company had reserved 3,632,996 shares of common stock for issuance upon the exercise of outstanding common stock options and 92,641 for issuance upon the vesting of restricted stock units.
	On July 22, 2013, the Company completed an underwritten public offering of 6,900,000 shares of the Company's common stock, which included the underwriter's exercise in full of its over-allotment option of 900,000 shares, at a price to the public of $10.40 per share. The Company's net proceeds from the sale of the shares, after deducting the underwriter's discount and offering expenses of $4.7 million, were $67.0 million.
	On September 28, 2012, we completed a registered direct public offering of 6,304,102 shares of our Common Stock to certain investors at a price of $4.07 per share, resulting in proceeds of $25.7 million.
	Warrant—In conjunction with entering into the Loan Agreement (See Note 7—Debt), the Company granted a warrant to the lender to purchase 329,932 shares of the Company's common stock at an exercise price of $2.94 per share. The fair value of the warrant of $0.8 million was calculated using the Black-Scholes warrant-pricing methodology at the date of issuance and was recorded as equity and as a discount to the debt and is being amortized to interest expense over the term of the related debt using the effective interest method. On April 30, 2013, the lender exercised the warrant in full via the "net issuance" method specified in the warrant agreement. In accordance with such provisions, the Company issued and delivered 223,431 shares of common shares to the lender on May 1, 2013. As a result of the exercise, the warrant is no longer outstanding and there are no additional shares issuable under this instrument.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2013
Stock-Based Compensation	'
Stock-Based Compensation	'
	9.        Stock-Based Compensation
	During 2013, the Company had three equity compensation plans: the 2013 Incentive Plan, which was approved by shareholders at the Company's Annual Meeting of Shareholders on May 23, 2013, the Amended and Restated 2000 Stock Incentive Plan, as amended (the "2000 Stock Incentive Plan") and the Amended and Restated 2000 Employee Stock Purchase Plan (the "Stock Purchase Plan"). Both the 2000 Stock Incentive Plan and the Stock Purchase Plan were adopted by the Company's Board of Directors in 2000. Upon the approval of the 2013 Incentive Plan, no additional awards will be issued under the 2000 Stock Incentive Plan and the shares remaining for future grant under the 2000 Stock Incentive Plan were transferred to the 2013 Incentive Plan.
	Under the terms of the 2013 Incentive Plan, the Company is authorized to grant a variety of incentive awards based on our common stock, including stock options (both incentive stock options and non-qualified stock options), performance shares and other stock awards, as well as the payment of incentive bonuses to all employees and non-employee directors. The 2013 Incentive Plan provides for a single aggregate per person annual sub-limit of 1,500,000 stock options, performance shares (including RSUs) and shares of restricted stock. The 2013 Incentive Plan provides for the issuance of a maximum of 3,053,833 shares of common stock. Shares subject to outstanding awards under the 2000 Stock Incentive Plan that are cancelled, expired, forfeited or otherwise not issued will also be added to the number of shares available under the 2013 Incentive Plan. As of December 31, 2013, 1,811,064 shares of the Company's common stock were reserved for future grants (or issuances) of restricted stock, restricted stock units, stock options, and stock warrants under the 2013 Incentive Plan. The 2013 Incentive Plan will terminate on April 16, 2023 unless it is extended or terminated earlier pursuant to its terms.
	Under the terms of the 2000 Stock Incentive Plan, the Company was authorized to grant a variety of incentive awards based on our common stock, including stock options, (both incentive stock options and non-qualified stock options), performance shares, and other stock awards to all employees and non-employee directors. On March 15, 2013, the Company's Board of Directors amended the 2000 Stock Incentive Plan to provide for a single aggregate per person annual sub-limit for the issuance of a maximum of 1,500,000 stock options, performance shares (including RSUs) and shares of restricted stock. The 2000 Stock Incentive Plan ceased to be available for additional grants once the Company's shareholders approved the 2013 Incentive Plan on May 23, 2013.
	On October, 31, 2013, the Company's Board of Directors terminated the Amended and Restated Insmed Incorporated 2000 Employee Stock Purchase Plan (the "Stock Purchase Plan"). Under the terms of the Stock Purchase Plan, employees were entitled to purchase common stock of the Company at a price equal to 85% of the fair market value of the shares on the purchase date. The Stock Purchase Plan was intended to qualify as an "employee stock purchase plan" within the meaning of Section 423 of the Internal Revenue Code. The foregoing description does not purport to be a complete description of the rights and obligations of the Company or the participants under the Stock Purchase Plan. The above description is qualified in its entirety by reference to the Stock Purchase Plan, a copy of which is included as Exhibit 10.22 in the Company's Annual Report on Form 10-K for the year ended December 31, 2006, filed with the Securities and Exchange Commission on March 16, 2007.
	During the first quarter of 2013, the Company completed a review of equity compensation awards granted under its 2000 Stock Incentive Plan and determined that it had inadvertently exceeded the annual per-person sub-limits involving certain awards previously made to certain of its current and past officers and directors (the "excess awards"). The aggregate amount of common stock represented by these excess awards, which consisted of RSUs and stock options, was approximately 1.4 million shares. These awards were deemed to be granted outside of the 2000 Stock Incentive Plan and as such the Company applied liability accounting to these awards. On May 23, 2013 (the date of the Company's 2013 Annual Meeting of Stockholders), shareholders approved the grants associated with the excess awards, which as of this date, allowed the excess awards to be deemed granted under the 2000 Stock Incentive Plan. As a result, the excess awards were remeasured at fair value on May 23, 2013 and the liability was reclassified to Additional paid-in capital. The unrecognized fair value calculated for the excess awards as of May 23, 2013 will be recognized as compensation expense ratably over the remaining requisite service period for each award.
	In connection with the appointment of the Company's Chief Commercial Officer on April 1, 2013, the Company made inducement grants of stock options totaling 300,000 shares of the Company's common stock.
	Stock Options—The Company calculates the fair value of stock options granted using the Black-Scholes valuation model. The Company calculated the fair value of stock options granted outside of the 2000 Stock Incentive Plan using liability accounting. These awards were classified as a liability and were remeasured at fair value at the end of each reporting period using the Black-Scholes valuation model and changes in fair value were included in compensation expense in the Consolidated Statements of Comprehensive Loss (see additional disclosures related to stock options granted outside the 2000 Stock Incentive Plan at the end of this footnote).
	The following table summarizes the grant date fair value and assumptions used in determining the fair value of stock options granted under and outside the 2013 Incentive Plan and the 2000 Stock Incentive Plan, as well as grants of inducement shares, during the years ended December 31, 2013, 2012 and 2011.
			2013		2012		2011
	Volatility		86.2% - 96.0%		99.1% - 107.1%		111.6% - 128.7%
	Risk-free interest rate		0.65% - 1.65%		0.57% - 0.99%		0.91% - 2.12%
	Dividend yield		0.00%		0.00%		0.00%
	Expected option term (in years)		6.25		6.25		6.25
	Weighted-average fair value of stock options granted		$8.16		$3.21		$2.68
	For the years ended December 31, 2013, 2012 and 2011, the volatility factor was based on the Company's historical volatility since the closing of the Merger on December 1, 2010. The expected life was determined using the simplified method as described in ASC Topic 718, "Accounting for Stock Compensation", which is the midpoint between the vesting date and the end of the contractual term. The risk-free interest rate is based on the US Treasury yield in effect at the date of grant. Forfeitures are based on actual percentage of option forfeitures since the closing of the Merger on December 1, 2010, and this is the basis for future forfeiture expectations.
	The following table summarizes stock option activity for stock options granted under the 2013 Incentive Plan and the 2000 Stock Incentive Plan, as well as grants of inducement shares, for the years ended December 31, 2013, 2012 and 2011 as follows:
			Number of			Weighted			Weighted			Aggregate
			Shares			Average			Average			Intrinsic
						Exercise			Remaining			Value
						Price			Contractual
									Life in Years
	Options outstanding at December 31, 2010			214,275		$	18.43
	Granted			766,000			3.77
	Exercised			(5,200	)		6.16
	Forfeited and expired			(83,324	)		26.57
	Options outstanding at December 31, 2011			891,751			5.15
	Vested and expected to vest at December 31, 2011			816,414			5.3
	Exercisable at December 31, 2011			125,751			13.54
	Options outstanding at December 31, 2011			891,751		$	5.15
	Granted			1,116,384			4.12
	Exercised			(30,250	)		7.08
	Forfeited and expired			(160,046	)		9.54
	Options outstanding at December 31, 2012			1,817,839			4.1
	Vested and expected to vest at December 31, 2012			1,692,915			4.11
	Exercisable at December 31, 2012			438,145			4.59
	Options outstanding at December 31, 2012			1,817,839		$	4.1
	Granted			2,323,500			10.53
	Exercised			(371,743	)		4.37
	Forfeited and expired			(136,600	)		10.49
	Options outstanding at December 31, 2013			3,632,996			7.94			8.93		$	32,903,657
	Vested and expected to vest at December 31, 2013			3,402,306			7.88			8.91		$	31,012,054
	Exercisable at December 31, 2013			484,213			4.25			7.36		$	6,176,106
	The total intrinsic value of stock options exercised during the years ended December 31, 2013, 2012 and 2011 was $2.7 million, $25 thousand and $23 thousand, respectively.
	As of December 31, 2013, there was $23.5 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted average period of 2.64 years. The following table summarizes the range of exercise prices and the number of stock options outstanding and exercisable as of December 31, 2013:
	Outstanding as of December 31, 2013														Exercisable as of
															December 31, 2013
	Range of						Number of			Weighted			Weighted		Number of		Weighted
	Exercise Prices						Options			Average			Average		Options		Average
										Remaining			Exercise Price				Exercise
										Contractual Term							Price
										(in years)
	$	3.03		$	3.29			296,687			7.46		$	3.04		153,089	$	3.04
	$	3.4		$	3.4			708,314			8.69		$	3.4		177,079	$	3.4
	$	3.48		$	6.65			423,595			8.41		$	5.55		125,045	$	5.64
	$	6.7		$	6.7			20,000			9.04		$	6.7		-		-
	$	6.9		$	6.9			381,200			8.98		$	6.9		10,000	$	6.9
	$	6.96		$	7.44			109,500			9.02		$	6.99		-		-
	$	7.45		$	7.45			375,000			9.25		$	7.45		-		-
	$	8.3		$	11.46			312,950			9.42		$	10.96		5,250	$	8.3
	$	12.44		$	12.44			565,050			9.16		$	12.44		13,750	$	12.44
	$	12.78		$	16.54			440,700			9.8		$	14.55		-		-
	Restricted Stock and Restricted Stock Units—The Company grants Restricted Stock ("RS") and Restricted Stock Units ("RSUs") to eligible employees, including our executives. Each RS and 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 granted under the Company's 2013 Incentive Plan and 2000 Stock Incentive Plan are generally valued at the market price of the Company's common stock on the date of grant. In the first quarter of 2011, the Company granted RSUs outside of the 2000 Stock Incentive Plan and those awards were accounted for as a liability as they would have been deemed to be cash settled until additional shares were authorized for issuance under the 2000 Stock Incentive Plan. In May 2011, additional shares under the 2000 Stock Incentive Plan were authorized and the RSUs were converted to equity awards and were valued at the market price of our common stock on that date. In addition, RSUs granted in excess of certain plan sub-limits were considered to be granted outside the 2000 Stock Incentive Plan and were classified as a liability and remeasured at fair value at the end of each reporting period and changes in fair value are included in compensation expense in the Consolidated Statements of Comprehensive Loss (see additional disclosures related to RSUs granted outside the 2000 Stock Incentive Plan at the end of this footnote). The Company recognizes noncash compensation expense for the fair values of these RS and RSUs on a straight-line basis over the requisite service period of these awards, which is generally three years.
The following table summarizes RSU awards granted under the 2013 Incentive Plan and the 2000 Stock Incentive Plan during the years ended December 31, 2013, 2012 and 2011:
		Number of			Weighted
		RSU's			Average
					Grant Price
Outstanding at December 31, 2010			-			-
Granted			491,255		$	6.36
Forfeited			(4,230	)		5.13
Outstanding at December 31, 2011			487,025			6.37
Granted			61,011			3.44
Released			(322,819	)		4.59
Forfeited			(9,692	)		5.69
Outstanding at December 31, 2012			215,525		$	6.26
Granted			55,317			6.77
Released			(177,316	)		6.42
Forfeited			(885	)		5
Outstanding at December 31, 2013			92,641		$	6.27
Expected to Vest			92,641		$	6.27
Awards Granted Outside of the 2000 Stock Incentive Plan—During the first quarter of 2013, the Company completed a review of equity compensation awards granted under its 2000 Stock Incentive Plan and determined that it had inadvertently exceeded the annual per-person sub-limits involving certain awards previously made to certain of its current and past officers and directors (the "excess awards"). The aggregate amount of common stock represented by these excess awards, which consisted of RSUs and stock options, was approximately 1.4 million shares. These awards were deemed to be granted outside of the 2000 Stock Incentive Plan and as such the Company applied liability accounting to these awards. On May 23, 2013 (the date of the Company's 2013 Annual Meeting of Stockholders), shareholders approved the grants associated with the excess awards, which as of this date, allowed the excess awards to be deemed granted under the 2000 Stock Incentive Plan. As a result, the excess awards were remeasured at fair value on May 23, 2013 and the liability was reclassified to Additional paid-in capital. The unrecognized fair value calculated for the excess awards as of May 23, 2013 will be recognized as compensation expense ratably over the remaining requisite service period for each award.
The following table summarizes the stock-based compensation recorded in the Consolidated Statements of Comprehensive Loss related to stock options and RSUs during the years ended December 31, 2013, 2012 and 2011:
				2013			2012			2011
				(in millions)
Research and development expenses				$	2.4		$	0.7		$	0.5
General and administrative expenses					6.3			2.3			1.1
		Total		$	8.7	-1	$	3		$	1.6
-1
Included in the $8.7 million is $3.3 million and $0.8 million of expense that resulted from the remeasurement of certain stock options and RSUs, respectively, that occurred during May 2013.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Taxes	'
Income Taxes	'
	10.        Income Taxes
	The benefit for income taxes was $1.2 million and the effective rate was 2.1% for the year ended December 31, 2013. The provision for income taxes was $0 and the effective rate was 0.0% during the years ended December 31, 2012 and 2011. The benefit for income taxes recorded and the effective tax rate for the year ended December 31, 2013 solely reflect the reversal of a valuation allowance previously recorded against the Company's New Jersey State net operating losses ("NOL") that resulted from the Company's sale of $27.0 million of its New Jersey State NOLs under the State of New Jersey's Technology Business Tax Certificate Transfer Program (the "Program") for cash of $1.2 million, net of commissions. The Program allows qualified technology and biotechnology businesses in New Jersey to sell unused amounts of NOLs and defined research and development tax credits for cash.
	The Company is subject to US federal and state income taxes. The Company has never been audited and the statute of limitations for tax audit is generally open for the years 2010 and later. However, except in 2009, the Company has incurred net operating losses since inception. Such loss carryforwards would be subject to audit in any tax year in which those losses are utilized, notwithstanding the year of origin. The Company's policy is to recognize interest accrued related to unrecognized tax benefits and penalties in income tax expense. The Company has recorded no such expense. As of December 31, 2013 and 2012, the Company has recorded no reserves for unrecognized income tax benefits, nor has it recorded any accrued interest or penalties related to uncertain tax positions. The Company does not anticipate any material changes in the amount of unrecognized tax positions over the next twelve months.
	The reconciliation between the federal statutory tax rate of 34% and the Company's effective tax rate is as follows:
		Years Ended
		December 31,
		2013			2012			2011
	Statutory federal tax rate		34	%		34	%		34	%
	Permanent items		-			-			(4	)%
	State income taxes, net of federal benefit		7	%		4	%		3	%
	Research and development credit		7	%		1	%		5	%
	Expired net operating loss carryforwards		-			(15	)%		(10	)%
	Change in state tax rate		2	%		-			-
	Change in valuation allowance		(49	)%		(22	)%		(27	)%
	Other		1	%		(2	)%		(1	)%
	Effective tax rate		2	%		0	%		0	%
	Deferred tax assets and liabilities are determined based on the difference between financial statement and tax bases using enacted tax rates in effect for the year in which the differences are expected to reverse. The components of the deferred tax assets and liabilities consist of the following:
		As of December 31,
		2013			2012
		(in thousands)
	Deferred tax assets:
	Net operating loss carryforwards	$	149,753		$	128,257
	General business credits		15,209			10,501
	Alternative Minimum Tax (AMT) credit		418			418
	Other		5,951			3,007
	Gross deferred tax assets	$	171,331		$	142,183
	Deferred tax liabilities:
	In-process research and development	$	(23,245	)	$	(22,093	)
	Deferred tax liabilities	$	(23,245	)	$	(22,093	)
	Net deferred tax assets	$	148,086		$	120,090
	Valuation Allowance		(148,086	)		(120,090	)
	Net deferred tax assets	$	-		$	-
	The net deferred tax assets (prior to applying the valuation allowance) of $148.1 million and $120.1 million at December 31, 2013 and 2012, respectively, primarily consist of net operating loss carryforwards for income tax purposes. Due to the Company's history of operating losses, the Company recorded a full valuation allowance on its net deferred tax assets by increasing the valuation allowance by $28.0 million as it is more likely than not that such tax benefits will not be realized.
	At December 31, 2013, the Company had federal net operating loss carryforwards for income tax purposes of approximately $398.7 million available to offset future taxable income, if any. The NOL carryovers and general business tax credits expire in various years beginning in 2018.
	Utilization of the Company's NOL and general business tax credit carryforwards generated in prior years through September 2012 (the "September 2012 and prior NOLs") are likely subject to substantial limitations under Section 382 of the Internal Revenue Code ("Section 382") due to ownership changes that occurred at various points during years prior to 2012 and during September 2012. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain shareholders or public groups in the stock of a corporation by more than 50 percentage points over a three-year period. Since the Company's formation, it has raised capital through the issuance of common stock on several occasions which, combined with the purchasing shareholders' subsequent disposition of those shares, likely resulted in multiple changes in ownership, as defined by Section 382 since the Company's formation in 1999. The substantial limitations on the use of the September 2012 and prior NOLs are likely to result in expiration of a substantial portion of these NOL or general business tax credit carryforwards before utilization which would substantially reduce the Company's gross deferred tax assets. The Company plans to complete a Section 382 analysis regarding the limitation of its NOL and general business tax credit carryforwards and intends to disclose the results of this analysis when it is completed.

License_and_Collaboration_Agre

License and Collaboration Agreements	12 Months Ended
	Dec. 31, 2013
License and Collaboration Agreements	'
License and Collaboration Agreements	'
	11.        License and Collaboration Agreements
	In-License Agreements
	Ipsen and Genentech—In March 2007, the Company was granted a license or sublicense as applicable to patents held by Ipsen and Genentech to develop IPLEX in certain medical indications in the US and foreign territories. In November 2008, the Company gained Royalty-Free Worldwide Rights for IPLEX from Ipsen and Genentech in connection with potential expanded access ALS programs.
	PARI Pharma GmbH—In April 2008, the Company entered into a licensing agreement with PARI Pharma GmbH for use of the optimized eFlow Nebulizer System for delivery of ARIKAYCE in treating patients with CF, bronchiectasis, and NTM infections. Insmed has rights to several US and foreign issued patents and patent applications involving improvements to the optimized eFlow Nebulizer System. In consideration of this agreement, PARI shall receive payments either in cash, qualified stock or a combination of both, at PARI's discretion, based on achievement of certain future milestone events including first acceptance of MAA submission (or equivalent) in the US of ARIKAYCE and the device, first receipt of marketing approval in the US for ARIKAYCE and the device, and first receipt of marketing approval in a major EU country for ARIKAYCE. In addition, PARI will receive royalty payments on commercial sales of ARIKAYCE.
	Out-License Agreements
	NAPO Pharmaceuticals—In January 2007, the Company entered into an agreement with NAPO Pharmaceuticals, whereby it granted NAPO a license for INSM-18 also known as Masoprocal. The license gives NAPO the right to develop, manufacture and commercialize Masoprocal products for any indications relating specifically to diabetes, cardiac disease, vascular disease, metabolic disease and Syndrome X. The agreement calls for payments from NAPO to the Company upon the achievement of certain milestones which have not yet been met.
	TriAct—In December, 2010, the Company entered into an agreement with TriAct Therapeutics Inc. ("TriAct") whereby it granted TriAct an exclusive license for INS-18 also known as Masoprocal. The license gives TriAct the right to develop, manufacture and commercialize Masoprocal products for any indications relating specifically to oncology. The agreement calls for the issue of TriAct common stock to Insmed upon the achievement of certain milestones. To date, no milestones have been achieved and no common stock has been received.
	Eleison—In February, 2011, the Company entered into an agreement with Eleison Pharmaceuticals whereby it granted Eleison an exclusive license for CISPLATIN Lipid Complex. The license gives Eleison the right to develop, manufacture and commercialize CISPLATIN Lipid Complex. Payments totaling $1.0 million were received in 2011 and were recorded as license fee revenue.
	Premacure (now Shire plc)—In May 2012, the Company entered into an agreement with Premacure (now Shire plc) pursuant to which the Company granted to Premacure an exclusive, worldwide license to develop, manufacture and commercialize IGF-1, with its natural binding protein, IGFBP-3, for the prevention and treatment of complications of preterm birth in exchange for royalty payments on commercial sales of IGF-1 (the "Premacure License Agreement"). In March 2013, we amended the Premacure License Agreement to provide Premacure with the option, exercisable by Premacure any time prior to April 30, 2013, to pay us $11.5 million (the "Buyout Amount") and assume any of our royalty obligations to other parties in exchange for a fully paid license. On April 29, 2013, Premacure exercised this option and paid the Company $11.5 million in exchange for a fully paid license. The Company recorded this payment as other revenue in the three months ended June 30, 2013. The Company is not entitled to any additional future royalties from Premacure, and Premacure has assumed the Company's royalty obligations to other parties under the Premacure License Agreement.
	Collaboration Agreements
	Cystic Fibrosis Foundation Therapeutics, Inc.—In 2004 and 2009, the Company entered into research funding agreements with Cystic Fibrosis Foundation Therapeutics, Inc. (CFFT) whereby it received $1.7 million and $2.2 million for each respective agreement in research funding for the development of its ARIKAYCE product. If ARIKAYCE becomes an approved product for CF in the US, the Company will owe payments totaling up to $13.4 million to CFFT that would be payable over a three-year period after approval as a commercialized drug in the US. Furthermore, if certain sales milestones are met within 5 years of the drug commercialization approval for CF in the US, the Company would owe an additional payment of $3.9 million. Since there is significant development risk associated with ARIKAYCE, we have not accrued these obligations.
	National Institutes of Allergy and Infectious Diseases—In 2009 and 2012, the Company entered into a cooperative research and development agreement (CRADA) with National Institute of Allergy and Infectious Diseases (NIAID) to design and conduct our phase 2 study of ARIKAYCE in patients with NTM. NIAID has also agreed to provide biostatistical advisory input in connection with the phase 2 NTM study. If the Company decides not to continue with the commercialization of ARIKAYCE in NTM, NIAID will have the right to complete the clinical trial. Further, NIAID may elect to pursue its rights to obtain license rights to certain inventions made under the CRADA.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies	'
Commitments and Contingencies	'
	12.        Commitments and Contingencies
	Commitments
	The Company has two operating leases for office and laboratory space located in Monmouth Junction, NJ through December 31, 2014. Future minimum rental payments under these two leases total approximately $0.7 million. The Company also has an operating lease for office and laboratory space located in Bridgewater, NJ that terminates in November 2019. Future minimum rental payments under this lease are $2.4 million. The Company also leases office space in Richmond, VA, where the Company's corporate headquarters were previously located, through October 2016. Future minimum rental payments under this lease total approximately $1.4 million. During 2011, the Company recorded a net present value charge of $1.2 million in general and administrative expenses associated with vacating the Richmond facility. The remaining accrual for this charge was $0.7 million as of December 31, 2013.
	Rent expense charged to operations was $1.0 million, $1.0 million, and $1.0 million for the years ended December 31, 2013, 2012 and 2011, respectively. Future minimum rental payments required under the Company's operating leases are as follows (in thousands):
	Year Ending in December 31:
	2014	$	1,237
	2015		944
	2016		886
	2017		474
	2018		488
	2019		460
		$	4,489
	Legal Proceedings
	Cacchillo v. Insmed
	On October 6, 2010, a complaint was filed against the Company by Angeline Cacchillo ("Plaintiff") in the U.S. District Court for the Northern District of New York (the "Court"), captioned Cacchillo v. Insmed, Inc., No. 1:10-cv-0199, seeking monetary damages and a court order requiring Insmed to support Plaintiff's compassionate use application to the FDA and if approved, to provide Plaintiff with IPLEX. Plaintiff was a participant in the phase II clinical trial of IPLEX sponsored by us evaluating the effectiveness of the investigational drug in patients with type 1 myotonic muscular dystrophy ("MMD"). In the complaint, Plaintiff alleged (i) violation of constitutional due process and equal protection by depriving Plaintiff of continued access to IPLEX, (ii) fraudulent inducement to enter the phase II clinical trial with the false promise to support Plaintiff's compassionate use application to the FDA, (iii) negligent representation that the Company would support Plaintiff's compassionate use application, (iv) breach of contract, seeking monetary and non-monetary damages, (v) intentional infliction of emotional distress by refusing to support Plaintiff's compassionate use application after providing IPLEX, (vi) violation of an assumed duty of care to Plaintiff, (vii) breach of fiduciary duty to Plaintiff, (viii) negligence and (ix) unjust enrichment. Plaintiff seeks compensatory and punitive monetary damages and sought injunction relief as noted above.
	On October 7, 2010, Plaintiff filed a motion for a preliminary injunction that would require us to provide a written statement supporting the "compassionate use" of IPLEX for Plaintiff and directing us to provide IPLEX to Plaintiff at cost in the event that the compassionate use application were granted by the FDA. On October 22, 2010, the Court denied Plaintiff's motion for the preliminary injunction concluding that the Court lacked subject matter jurisdiction with respect to her claim for a preliminary injunction. Plaintiff appealed the Court's denial of her motion for a preliminary injunction to the U.S. Court of Appeals for the Second Circuit, which affirmed the trial court's order denying the Plaintiff's motion for a preliminary injunction.
	We filed a motion with the Court to dismiss all of the outstanding claims, and on June 29, 2011, the Court dismissed six of Plaintiff's claims, leaving outstanding the claims for (i) fraudulent inducement, (ii) negligent misrepresentation, and (iii) breach of contract. The Company filed an answer and affirmative defenses with the Court on July 12, 2011. Plaintiff's claim for monetary damages with respect to these claims remains outstanding. The parties completed discovery on or about June 1, 2012. The Company filed a Motion for Summary Judgment on August 1, 2012 seeking judgment in our favor on the three claims remaining in the case and the motion was fully submitted on October 9, 2012. On January 19, 2013, the Court granted the Company's Motion for Summary Judgment and dismissed all of the outstanding claims. Plaintiff appealed the Court's decision to the U.S. Court of Appeals for the Second Circuit and, on January 7, 2014, the Court affirmed the decision to dismiss all outstanding claims.
	Pilkiewicz v. Transave LLC
	On March 28, 2011, Frank G. Pilkiewicz and other former stockholders of Transave (collectively, the "Petitioners") filed an appraisal action against the Company's subsidiary Transave, LLC in the Delaware Court of Chancery captioned Frank G. Pilkiewicz, et al. v. Transave, LLC , C.A. No. 6319-CS. On December 13, 2011, following the mailing of the revised notice of appraisal rights in accordance with the settlement terms of Mackinson et al. v. Insmed, an Amended Petition for Appraisal of Stock was filed by the Petitioners.
	The Petitioners seek appraisal under Delaware law of their total combined common stock holdings representing total dissenting shares of approximately 7.77 million shares of Transave, Inc. common stock (the "Transave Stock"). The Petitioners are challenging the value of the consideration that they would be entitled to receive for their Transave Stock under the terms of the merger.
	Under the terms of the merger agreement, certain of the former stockholders of Transave (the "Transave Stockholders") are obligated to indemnify the Company for certain liabilities in connection with the appraisal action. The Company notified the Transave Stockholders in May 2012 that the Company is seeking indemnification in accordance with the merger agreement and that it will continue to retain the aggregate amount of the holdback shares totaling 1,765,271 shares, as security for any indemnification payments due under the merger agreement. Discovery is complete and the trial is scheduled to begin in April 2014. The Company believes that the allegations contained in the amended petition are without merit and we intend to continue to vigorously defend this action. It is not possible at this time to estimate the amount of loss or range of possible loss, if any, that might result from an adverse resolution of this action.
	From time to time, the Company is a party to various other lawsuits, claims and other legal proceedings that arise in the ordinary course of our business. While the outcomes of these matters are uncertain, management does not expect that the ultimate costs to resolve these matters will have a material adverse effect on the Company's consolidated financial position, results of operations or cash flows.

Quarterly_Financial_Data_Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Data (Unaudited)	'
Quarterly Financial Data (Unaudited)	'
	13.        Quarterly Financial Data (Unaudited)
	The following table summarizes unaudited quarterly financial data for the years ended December 31, 2013 and 2012 (in thousands, except per share data).
		2013
		First			Second			Third			Fourth			Total
		Quarter			Quarter			Quarter			Quarter
	Revenues	$	-		$	11,500		$	-		$	-		$	11,500
	Operating loss		(14,309	)		(8,270	)		(16,842	)		(15,594	)		(55,015	)
	Net loss		(13,678	)		(8,854	)		(17,327	)		(16,214	)		(56,073	)
	Basic and diluted net loss attributable to common stockholders per common share	$	(0.43	)	$	(0.28	)	$	(0.46	)	$	(0.41	)	$	(1.60	)
		2012
		First			Second			Third			Fourth			Total
		Quarter			Quarter			Quarter			Quarter
	Revenues	$	-		$	-		$	-		$	-		$	-
	Operating loss		(7,264	)		(9,983	)		(9,353	)		(15,838	)		(42,438	)
	Net loss		(6,845	)		(9,696	)		(9,382	)		(15,451	)		(41,374	)
	Basic and diluted net income (loss) attributable to common stockholders per common share	$	(0.28	)	$	(0.39	)	$	(0.38	)	$	(0.49	)	$	(1.56	)
	Basic and diluted net income (loss) per share amounts included in the above tables are computed independently for each of the quarters presented. Accordingly, the sum of the quarterly basic and diluted net loss per share amounts may not agree to the total for the year.

Retirement_Plan

Retirement Plan	12 Months Ended
	Dec. 31, 2013
Retirement Plan	'
Retirement Plan	'
	14.        Retirement Plan
	The Company has a 401(k) defined contribution plan for the benefit for all employees and permits voluntary contributions by employees subject to IRS-imposed limitations. There were no employer contributions in 2013, 2012 and 2011.

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2013
Subsequent Events	'
Subsequent Events	'
	15.        Subsequent Events
	On February 10, 2014, the Company entered into a Contract Manufacturing Agreement (the "Agreement") with Therapure Biopharma Inc. ("Therapure") for the manufacture of the Company's product ARIKAYCE, liposomal amikacin for inhalation. Pursuant to the Agreement, the Company and Therapure will collaborate to construct a production and quality control area for the manufacture and testing of ARIKAYCE in Therapure's existing manufacturing facility in Mississauga, Ontario, Canada. Therapure will manufacture ARIKAYCE for the Company on a non-exclusive basis. The Agreement has an initial term of five years from the first date on which Therapure delivers ARIKAYCE to Insmed after Insmed obtains permits related to the manufacture of ARIKAYCE, and will renew automatically for successive periods of two years each, unless terminated by either party by providing the required two years' prior written notice to the other party. Notwithstanding the foregoing, the parties have rights and obligations under the Agreement prior to the commencement of the initial term. The Agreement allows for termination by either party upon the occurrence of certain events, including, (i) the material breach by the other party of any provision of the Agreement or the Quality Agreement expected to be entered into between the parties, or (ii) the default or bankruptcy of the other party. In addition, the Company may terminate the Agreement for any reason upon no fewer than one hundred eighty days' advance notice.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Use of Estimates	'
	Use of Estimates—The preparation of the consolidated financial statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. The Company bases its estimates and judgments on historical experience and on various other assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company's balance sheets and the amounts of revenue and expenses reported for each period presented are effected by estimates and assumptions, which are used for, but not limited to, the accounting for revenue recognition, stock-based compensation, income taxes, loss contingencies, the beneficial conversion charge, the warrant fair value calculation, impairment of intangibles and long lived assets and accounting for research and development costs. Actual results could differ from those estimates.
Prior Period Reclassifications	'
	Prior Period Reclassifications—Certain amounts in the 2011 consolidated financial statements were reclassified to conform to the 2012 presentation. Specifically, the Company allocated a portion of certain operating expenses from general and administrative expense to research and development expense in 2012 and recast the 2011 amounts to conform to the current year presentation for comparability purposes.
Investment Income and Interest Expense	'
	Investment Income and Interest Expense—Investment income consists of interest and dividend income earned on our cash, cash equivalents and short-term investments, along with realized gains (losses) on the sale of investments. Interest expense consists primarily of interest costs related to our debt and capital lease obligations.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents—The Company considers cash equivalents to be highly liquid investments with maturities of three months or less from the date of purchase.
Fixed Assets, Net	'
	Fixed Assets, Net—Fixed assets are recorded at cost and are depreciated on a straight-line basis over the estimated useful lives of the assets. Estimated useful lives of three to seven years are used for computer equipment, laboratory equipment, office equipment and furniture and fixtures. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset. Long-lived assets, such as lab equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, then an impairment charge is recognized for the amount by which the carrying value of the asset exceeds the fair value of the asset.
Identifiable Intangible Assets	'
	Identifiable Intangible Assets—Identifiable intangible assets are measured at their respective fair values and are not amortized until commercialization. Once commercialization occurs, these intangible assets will be amortized over their estimated useful lives. The fair values assigned to the Company's intangible assets are based on reasonable estimates and assumptions given available facts and circumstances. Unanticipated events or circumstances may occur that may require the Company to review the assets for impairment. Events or circumstances that may require an impairment assessment include negative clinical trial results, the non-approval of a new drug application by a regulatory agency, material delays in our development program or a sustained decline in market capitalization.
	Indefinite-lived intangible assets are not subject to periodic amortization. Rather, indefinite-lived intangibles are reviewed for impairment by applying a fair value based test on an annual basis or more frequently if events or circumstances indicate impairment may have occurred. Events or circumstances that may require an interim impairment assessment are consistent with those described above. The Company performs its annual impairment test as of October 1 of each year.
	The Company uses the income approach to derive the fair value of in-process research and development assets. This approach calculates fair value by estimating future cash flows attributable to the assets and then discounting these cash flows to a present value using a risk-adjusted discount rate. A market based valuation approach was not considered given a lack of revenues and profits for the Company. This approach requires significant management judgment with respect to unobservable inputs such as future volume, revenue and expense growth rates, changes in working capital use, appropriate discount rates and other assumptions and estimates. The estimates and assumptions used are consistent with the Company's business plans.
Debt Issuance Costs	'
	Debt Issuance Costs—Debt issuance costs are amortized using the effective interest rate method, and amortized to interest expense over the term of the debt. Debt issuance costs paid to the lender are reflected as a discount to the debt, and debt issuance costs paid to other third parties are reflected as other assets in the consolidated balance sheets.
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 judgments 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 are categorized in the tables below 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 following table presents assets and liabilities measured at fair value as of December 31, 2013 and December 31, 2012 (in thousands).
		Fair Value Measurements at Reporting Date Using
		Total			Quoted Prices in			Quoted Prices in			Significant
					Active Markets for			Inactive Markets for			Unobservable Inputs
					Identical Assets			Identical Assets			(Level 3)
					(Level 1)			(Level 2)
	As of December 31, 2013:
	Assets:
	Cash and cash equivalents	$	113,894		$	113,894		$	-		$	-
		$	113,894		$	113,894		$	-		$	-
	As of December 31, 2012:
	Assets:
	Cash and cash equivalents	$	90,782		$	90,782		$	-		$	-
	Certificate of deposit		2,153			2,153			-			-
		$	92,935		$	92,935		$	-		$	-
	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 a maturity of three months or less from the date of purchase and the short-term investments consist of instruments with maturities greater than three months.
	We recognize 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 2013 and 2012.
	As of December 31, 2013 and 2012, the Company held no securities that were in an unrealized loss or gain position. The Company's unrealized loss on investments for the years ended 2012 and 2011 of $0.5 million and $0.5 million, respectively, previously were presented incorrectly as zero and a gain of $0.5 million, respectively, in the prior year's Consolidated Statements of Comprehensive Loss. The Company's comprehensive loss is now correctly presented. There was no impact on net loss during either period as a result of the correction of these immaterial clerical errors. During 2012, the Company realized a net gain of $0.8 million from the sale of short term investments.
	The Company reviews the status of each security quarterly to determine whether an other-than-temporary impairment has occurred. In making our determination, we consider 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) our ability and intent to retain the investment for a sufficient period of time for it to recover.
Concentration of Credit Risk	'
	Concentration of Credit Risk—Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents and short-term investments. The Company places its cash equivalents with high credit-quality financial institutions and may invest its short-term investments in US treasury securities, mutual funds and government agency bonds. The Company has established guidelines relative to credit ratings and maturities that seek to maintain safety and liquidity.
	The Company sources its raw materials from single suppliers. In addition, the production of the Company's product candidate is performed by a sole manufacturer. The inability of the suppliers or manufacturer to fulfill supply requirements of the Company could materially impact future operating results. A change in the relationship with the suppliers or manufacturer, or an adverse change in their business, could materially impact future operating results.
Revenue Recognition	'
	Revenue Recognition—In 2013, the Company's other revenue solely consists of an $11.5 million payment received from Premacure (now Shire plc) in exchange for the Company's right to receive royalties under its license agreement with Premacure. We recorded this as other revenue after all four revenue recognition criteria were present and the Company had no continuing performance obligations related to the payment received. The Company's revenues in 2011 were from (1) $3.4 million of cost recovery revenues from the use of IPLEX® in an Expanded Access Program (EAP) the Company established in Italy to provide IPLEX® to physicians for use in their patients with Amyotrophic Lateral Sclerosis (ALS) (this program was discontinued in December 2011), and (2) a $1.0 million non-refundable upfront license payment received from Eleison Pharmaceuticals, Inc. (Eleison") for the licensing of the Company's lipid-complexed cisplatin and/or liposomal cisplatin products and technology to Eleison. We recorded this revenue during 2011 as we had the contractual right to receive it and we have no continuing involvement under this licensing agreement.
	The Company recognizes revenues when all of the following four criteria are present: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; the fee is fixed or determinable; and collectability is reasonably assured.
	Where the Company has continuing performance obligations under the terms of a collaborative arrangement, non-refundable upfront license payments received upon contract signing are recorded as deferred revenue and recognized as revenue as the related activities are performed. The period over which these activities are to be performed is based upon management's estimate of the development period. Changes in management's estimate could change the period over which revenue is recognized. Research and/or development payments are recognized as revenues as the related research and/or development activities are performed and when the Company has no continuing performance obligations related to the research and development payment received.
	Where the Company has no continuing involvement under a collaborative arrangement, the Company records nonrefundable license fee revenues when the Company has the contractual right to receive the payment, in accordance with the terms of the collaboration agreement, and records milestones upon appropriate notification to the Company of achievement of the milestones by the collaborative partner.
	The Company recognizes revenue from milestone payments when earned, provided that (i) the milestone event is substantive and its achievability was not reasonably assured at the inception of the agreement and (ii) the Company does not have ongoing performance obligations related to the achievement of the milestone earned. Milestone payments are considered substantive if all of the following conditions are met: the milestone payment (a) is commensurate with either the vendor's performance to achieve the milestone or the enhancement of the value of the delivered item or items as a result of a specific outcome resulting from the vendor's performance to achieve the milestone, (b) relates solely to past performance, and (c) is reasonable relative to all of the deliverables and payment terms (including other potential milestone consideration) within the arrangement. Any amounts received under the agreement in advance of performance, if deemed substantive, are recorded as deferred revenue and recognized as revenue as the Company completes its performance obligations.
	With regard to recognizing revenue for multiple deliverable revenue arrangements, each deliverable within a multiple-deliverable revenue arrangement is accounted for as a separate unit of accounting if both of the following criteria are met: (1) the delivered item or items have value to the customer on a standalone basis and (2) for an arrangement that includes a general right of return relative to the delivered item(s), delivery or performance of the undelivered item(s) is considered probable and substantially in our control.
	In addition, multiple deliverable revenue arrangement consideration is allocated at the inception of an arrangement to all deliverables using the relative selling price method. The Company also applies a selling price hierarchy for determining the selling price of a deliverable, which includes (1) vendor-specific objective evidence, if available, (2) third-party evidence, if vendor-specific objective evidence is not available, and (3) estimated selling price if neither vendor-specific nor third-party evidence is available.
	Deferred revenue associated with a non-refundable payment received under a collaborative agreement that is terminated prior to its completion results in an immediate recognition of the deferred revenue.
Research and Development	'
	Research and Development—Research and development expenses consist primarily of salaries, benefits and other related costs, including stock based compensation, for personnel serving in our research and development functions, and other internal operating expenses, the cost of manufacturing our drug candidate, including the medical devices for drug delivery, for clinical study, the cost of conducting clinical studies, and the cost of conducting preclinical and research activities. The Company's expenses related to manufacturing its drug candidate and medical devices for clinical study are primarily related to activities at contract manufacturing organizations that manufacture ARIKAYCE and the medical devices for the Company's use. The Company's expenses related to clinical trials are primarily related to activities at contract research organizations that conduct and manage clinical trials on the Company's behalf. These contracts set forth the scope of work to be completed at a fixed fee or amount per patient enrolled. Payments under these contracts primarily depend on performance criteria such as the successful enrollment of patients or the completion of clinical trial milestones as well as time-based fees. Expenses are accrued based on contracted amounts applied to the level of patient enrollment and to activity according to the clinical trial protocol. Nonrefundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized. Such amounts are then recognized as an expense as the related goods are delivered or the services are performed, or when the goods or services are no longer expected to be provided.
Stock-Based Compensation	'
	Stock-Based Compensation—The Company recognizes stock-based compensation expense for awards of equity instruments to employees and directors based on the grant-date fair value of those awards. The grant-date fair value of the award is recognized as compensation expense ratably over the requisite service period, which generally equals the vesting period of the award, and if applicable, is adjusted for expected forfeitures. We also grant performance-based stock options to employees. The grant-date fair value of the performance-based stock options is recognized as compensation expense over the implicit service period using the accelerated attribution method once it is probable that the performance condition will be achieved. Stock-based compensation expense is included in both research and development expenses and general and administrative expenses in the Consolidated Statements of Comprehensive Loss.
	Certain awards deemed to be granted outside of the Company's equity incentive plans require the Company to use liability accounting. These awards are classified as a liability and are remeasured at fair value at the end of each reporting period until such time they are deemed to be granted under the Company's equity incentive plans. Changes in fair value are included in compensation expense in the Consolidated Statements of Comprehensive Loss (see additional disclosures related to awards granted outside of the 2000 Stock Incentive Plan in Footnote 9, Stock-Based Compensation).
Income Taxes	'
	Income Taxes—The Company accounts for income taxes under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date.
	A valuation allowance is recorded to reduce the deferred tax assets to the amount that is expected to be realized. In evaluating the need for a valuation allowance, we take into account various factors, including the expected level of future taxable income and available tax planning strategies. If actual results differ from the assumptions made in the evaluation of our valuation allowance, we record a change in valuation allowance through income tax expense in the period such determination is made.
	The Company uses a comprehensive model for how it measures, presents and discloses an uncertain tax position taken or expected to be taken in a tax return. The Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by taxing authorities, based solely on the technical merits of the position. The tax benefits recognized in the financial statements from such a position should be measured based on the largest benefit that has a greater than 50% likelihood to be sustained upon ultimate settlement. The Company has no uncertain tax positions as of December 31, 2013 that qualify for either recognition or disclosure in the consolidated financial statements.
	The Company's policy for interest and penalties related to income tax exposures is to recognize interest and penalties as a component of the income taxes on continuing operations in the Consolidated Statements of Comprehensive Loss.
Net Loss Per Common Share	'
	Net Loss Per Common Share—Basic net loss per common share is computed by dividing net loss attributable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted net loss per common share is computed by dividing net loss attributable to common stockholders 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 and warrants to purchase common stock would be antidilutive as the Company incurred a net loss. Potentially dilutive common shares resulting from the assumed exercise of outstanding stock options and warrants are determined based on the treasury stock method.
	The following table sets forth the reconciliation of the weighted average number of shares attributable to common stockholders used to compute basic net loss per share for the years ended December 31, 2013, 2012 and 2011.
		Twelve Months Ended December 31,
		2013			2012			2011
		(In thousands, except per share amounts)
	Numerator:
	Net loss attributable to common stockholders:	$	(56,073	)	$	(41,374	)	$	(68,839	)
	Denominator:
	Weighted average common shares used in calculation of basic net loss per share:		34,980			26,545			23,348
	Effect of dilutive securities:
	Common stock options		-			-			-
	Restricted stock and restricted stock units		-			-			-
	Common stock warrant		-			-			-
	Weighted average common shares outstanding used in calculation of diluted net loss per share		34,980			26,545			23,348
	Net loss per share:
	Basic and Diluted	$	(1.60	)	$	(1.56	)	$	(2.95	)
	The following potentially dilutive securities have been excluded from the computations of diluted weighted-average common shares outstanding as of December 31, 2013, 2012 and 2011 as their effect would have been anti-dilutive (in thousands).
		2013			2012			2011
	Warrants to purchase common stock		-			330			158
	Stock options to purchase common stock		3,633			1,818			892
	Restricted stock and restricted stock units		93			216			487
Segment Information	'
	Segment Information—The Company currently operates in one business segment, which is the development and commercialization of inhaled therapies for patients with serious lung diseases. A single management team that reports to the Chief Executive Officer comprehensively manages the entire business. The Company does not operate separate lines of business with respect to its products or product candidates. Accordingly, the Company does not have separate reportable segments.
Recently Adopted Accounting Pronouncements	'
	Recently Adopted Accounting Pronouncements—In February 2013, an Accounting Standards Update was issued that requires companies to present either in a single note or parenthetically on the face of the financial statements, the effect of significant amounts reclassified from each component of accumulated other comprehensive income (loss) based on its source and the income statement line items affected by the reclassification. This guidance is effective for annual and interim reporting periods beginning after December 15, 2012. This became effective for the Company on January 1, 2013 and its adoption did not impact the Company's consolidated financial statements.
	In July 2012, an Accounting Standards Update was issued that allows companies to assess qualitative factors to determine the likelihood of indefinite-lived intangible asset impairment and whether it is necessary to perform the quantitative impairment test currently required. This guidance is effective for annual and interim impairment tests performed for fiscal years beginning after September 15, 2012, with early adoption permitted. This became effective for us on January 1, 2013 and its adoption did not impact the Company's consolidated financial statements.
	In December 2011, an Accounting Standards Update was issued that requires disclosure of information about offsetting assets and liabilities and related arrangements to enable users of the Company's consolidated financial statements to understand the effect of those arrangements on the Company's financial position. The new guidance is effective for annual reporting periods beginning on or after January 1, 2013, and interim periods within those annual periods. This became effective for the Company on January 1, 2013 and its adoption did not impact the Company's consolidated financial statements.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Assets and liabilities measured on recurring basis	'
		Fair Value Measurements at Reporting Date Using
		Total			Quoted Prices in			Quoted Prices in			Significant
					Active Markets for			Inactive Markets for			Unobservable Inputs
					Identical Assets			Identical Assets			(Level 3)
					(Level 1)			(Level 2)
	As of December 31, 2013:
	Assets:
	Cash and cash equivalents	$	113,894		$	113,894		$	-		$	-
		$	113,894		$	113,894		$	-		$	-
	As of December 31, 2012:
	Assets:
	Cash and cash equivalents	$	90,782		$	90,782		$	-		$	-
	Certificate of deposit		2,153			2,153			-			-
		$	92,935		$	92,935		$	-		$	-
Reconciliation of the weighted average number of shares used to compute basic and diluted net loss per share	'
		Twelve Months Ended December 31,
		2013			2012			2011
		(In thousands, except per share amounts)
	Numerator:
	Net loss attributable to common stockholders:	$	(56,073	)	$	(41,374	)	$	(68,839	)
	Denominator:
	Weighted average common shares used in calculation of basic net loss per share:		34,980			26,545			23,348
	Effect of dilutive securities:
	Common stock options		-			-			-
	Restricted stock and restricted stock units		-			-			-
	Common stock warrant		-			-			-
	Weighted average common shares outstanding used in calculation of diluted net loss per share		34,980			26,545			23,348
	Net loss per share:
	Basic and Diluted	$	(1.60	)	$	(1.56	)	$	(2.95	)
Potentially dilutive securities excluded from computations of diluted weighted-average shares outstanding	'
		2013			2012			2011
	Warrants to purchase common stock		-			330			158
	Stock options to purchase common stock		3,633			1,818			892
	Restricted stock and restricted stock units		93			216			487

Accrued_Expenses_Tables

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2013
Accrued Expenses	'
Accrued Expenses	'
		As of December 31,
		2013		2012
		(in thousands)
	Accrued clinical trial expenses	$	2,484	$	1,460
	Accrued technical operation expenses		1,220		-
	Liability for stock-based compensation awards		-		1,204
	Accrued professional fees		24		185
	Accrued interest payable		159		80
	Other accrued expenses		18		4
		$	3,905	$	2,933

Fixed_Assets_net_Tables

Fixed Assets, net (Tables)	12 Months Ended
	Dec. 31, 2013
Fixed Assets, net	'
Schedule of fixed assets	'
			As of December 31,
		Estimated
	Asset Description	Useful Life (years)	2013			2012
			(in thousands)
	Lab equipment	7	$	3,371		$	2,872
	Furniture and fixtures	7		65			65
	Computer hardware and software	3 - 5		718			588
	Office equipment	7		117			117
	Manufacturing Equipment	7		375			325
	Leasehold improvements	lease term		612			581
	Construction in Progress (CIP)			116			-
				5,374			4,548
	Less accumulated depreciation and amortization			(3,562	)		(2,882	)
	Fixed assets, net		$	1,812		$	1,666

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2013
Debt	'
Components of the Company's debt balances	'
		December 31, 2013
		(in thousands)
	Debt:
	Notes payable	$	20,000
	Accretion of end of term charge		204
	Issuance fees paid to lender		(215	)
	Discount from warrant		(368	)
	Current portion of long-term debt		(3,283	)
	Long-term debt	$	16,338
Future principal repayments of the Notes	'
	Future principal repayments of the two Notes are as follows (in thousands):
	Year Ending in December 31:
	2014	$	3,626
	2015		7,785
	2016		8,589
		$	20,000

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2013
Stock-Based Compensation	'
Summary of grant date fair value and assumptions used in determining fair value of stock options	'
			2013		2012		2011
	Volatility		86.2% - 96.0%		99.1% - 107.1%		111.6% - 128.7%
	Risk-free interest rate		0.65% - 1.65%		0.57% - 0.99%		0.91% - 2.12%
	Dividend yield		0.00%		0.00%		0.00%
	Expected option term (in years)		6.25		6.25		6.25
	Weighted-average fair value of stock options granted		$8.16		$3.21		$2.68
Summary of stock option activity	'
			Number of			Weighted			Weighted			Aggregate
			Shares			Average			Average			Intrinsic
						Exercise			Remaining			Value
						Price			Contractual
									Life in Years
	Options outstanding at December 31, 2010			214,275		$	18.43
	Granted			766,000			3.77
	Exercised			(5,200	)		6.16
	Forfeited and expired			(83,324	)		26.57
	Options outstanding at December 31, 2011			891,751			5.15
	Vested and expected to vest at December 31, 2011			816,414			5.3
	Exercisable at December 31, 2011			125,751			13.54
	Options outstanding at December 31, 2011			891,751		$	5.15
	Granted			1,116,384			4.12
	Exercised			(30,250	)		7.08
	Forfeited and expired			(160,046	)		9.54
	Options outstanding at December 31, 2012			1,817,839			4.1
	Vested and expected to vest at December 31, 2012			1,692,915			4.11
	Exercisable at December 31, 2012			438,145			4.59
	Options outstanding at December 31, 2012			1,817,839		$	4.1
	Granted			2,323,500			10.53
	Exercised			(371,743	)		4.37
	Forfeited and expired			(136,600	)		10.49
	Options outstanding at December 31, 2013			3,632,996			7.94			8.93		$	32,903,657
	Vested and expected to vest at December 31, 2013			3,402,306			7.88			8.91		$	31,012,054
	Exercisable at December 31, 2013			484,213			4.25			7.36		$	6,176,106
Summary of range of exercise prices and the number of stock options outstanding and exercisable	'
	Outstanding as of December 31, 2013														Exercisable as of
															December 31, 2013
	Range of						Number of			Weighted			Weighted		Number of		Weighted
	Exercise Prices						Options			Average			Average		Options		Average
										Remaining			Exercise Price				Exercise
										Contractual Term							Price
										(in years)
	$	3.03		$	3.29			296,687			7.46		$	3.04		153,089	$	3.04
	$	3.4		$	3.4			708,314			8.69		$	3.4		177,079	$	3.4
	$	3.48		$	6.65			423,595			8.41		$	5.55		125,045	$	5.64
	$	6.7		$	6.7			20,000			9.04		$	6.7		-		-
	$	6.9		$	6.9			381,200			8.98		$	6.9		10,000	$	6.9
	$	6.96		$	7.44			109,500			9.02		$	6.99		-		-
	$	7.45		$	7.45			375,000			9.25		$	7.45		-		-
	$	8.3		$	11.46			312,950			9.42		$	10.96		5,250	$	8.3
	$	12.44		$	12.44			565,050			9.16		$	12.44		13,750	$	12.44
	$	12.78		$	16.54			440,700			9.8		$	14.55		-		-
Summary of RSU activity	'
			Number of			Weighted
			RSU's			Average
						Grant Price
	Outstanding at December 31, 2010			-			-
	Granted			491,255		$	6.36
	Forfeited			(4,230	)		5.13
	Outstanding at December 31, 2011			487,025			6.37
	Granted			61,011			3.44
	Released			(322,819	)		4.59
	Forfeited			(9,692	)		5.69
	Outstanding at December 31, 2012			215,525		$	6.26
	Granted			55,317			6.77
	Released			(177,316	)		6.42
	Forfeited			(885	)		5
	Outstanding at December 31, 2013			92,641		$	6.27
	Expected to Vest			92,641		$	6.27
Summary of stock-based compensation recorded in the Consolidated Statements of Comprehensive Loss	'
					2013			2012			2011
					(in millions)
	Research and development expenses				$	2.4		$	0.7		$	0.5
	General and administrative expenses					6.3			2.3			1.1
			Total		$	8.7	-1	$	3		$	1.6
	-1
	Included in the $8.7 million is $3.3 million and $0.8 million of expense that resulted from the remeasurement of certain stock options and RSUs, respectively, that occurred during May 2013.

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Taxes	'
Reconciliation between The Federal Statutory Tax Rate and Effective Tax Rate	'
		Years Ended
		December 31,
		2013			2012			2011
	Statutory federal tax rate		34	%		34	%		34	%
	Permanent items		-			-			(4	)%
	State income taxes, net of federal benefit		7	%		4	%		3	%
	Research and development credit		7	%		1	%		5	%
	Expired net operating loss carryforwards		-			(15	)%		(10	)%
	Change in state tax rate		2	%		-			-
	Change in valuation allowance		(49	)%		(22	)%		(27	)%
	Other		1	%		(2	)%		(1	)%
	Effective tax rate		2	%		0	%		0	%
Deferred Tax Assets and Liabilities	'
		As of December 31,
		2013			2012
		(in thousands)
	Deferred tax assets:
	Net operating loss carryforwards	$	149,753		$	128,257
	General business credits		15,209			10,501
	Alternative Minimum Tax (AMT) credit		418			418
	Other		5,951			3,007
	Gross deferred tax assets	$	171,331		$	142,183
	Deferred tax liabilities:
	In-process research and development	$	(23,245	)	$	(22,093	)
	Deferred tax liabilities	$	(23,245	)	$	(22,093	)
	Net deferred tax assets	$	148,086		$	120,090
	Valuation Allowance		(148,086	)		(120,090	)
	Net deferred tax assets	$	-		$	-

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies	'
Future minimum rental payments required under operating leases	'
	Future minimum rental payments required under the Company's operating leases are as follows (in thousands):
	Year Ending in December 31:
	2014	$	1,237
	2015		944
	2016		886
	2017		474
	2018		488
	2019		460
		$	4,489

Quarterly_Financial_Data_Unaud1

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
Quarterly Financial Data (Unaudited)	'
Quarterly financial data (Unaudited)	'
	The following table summarizes unaudited quarterly financial data for the years ended December 31, 2013 and 2012 (in thousands, except per share data).
		2013
		First			Second			Third			Fourth			Total
		Quarter			Quarter			Quarter			Quarter
	Revenues	$	-		$	11,500		$	-		$	-		$	11,500
	Operating loss		(14,309	)		(8,270	)		(16,842	)		(15,594	)		(55,015	)
	Net loss		(13,678	)		(8,854	)		(17,327	)		(16,214	)		(56,073	)
	Basic and diluted net loss attributable to common stockholders per common share	$	(0.43	)	$	(0.28	)	$	(0.46	)	$	(0.41	)	$	(1.60	)
		2012
		First			Second			Third			Fourth			Total
		Quarter			Quarter			Quarter			Quarter
	Revenues	$	-		$	-		$	-		$	-		$	-
	Operating loss		(7,264	)		(9,983	)		(9,353	)		(15,838	)		(42,438	)
	Net loss		(6,845	)		(9,696	)		(9,382	)		(15,451	)		(41,374	)
	Basic and diluted net income (loss) attributable to common stockholders per common share	$	(0.28	)	$	(0.39	)	$	(0.38	)	$	(0.49	)	$	(1.56	)

Description_of_Business_and_Ba1

Description of Business and Basis of Presentation (Details)	12 Months Ended
	Dec. 31, 2013
	item
Description of Business and Basis of Presentation	'
Number of initial indications in orphan patient populations for which clinical trials of ARIKAYCE is conducted	2

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details) (Computer equipment, laboratory equipment, office equipment and furniture and fixtures)	12 Months Ended
	Dec. 31, 2013
Minimum	'
Fixed Assets, Net	'
Estimated useful live of fixed assets	'3 years
Maximum	'
Fixed Assets, Net	'
Estimated useful live of fixed assets	'7 years

Summary_of_Significant_Account4

Summary of Significant Accounting Policies (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Assets measured at fair value	'	'	'
Certificate of deposit	$2,153,000	'	'
Securities that were in an unrealized loss or gain position	0	'	0
Gain on sale of short-term investments	833,000	'	'
Unrealized gain (loss) on investments	-450,000	-543,000	'
Previously reported	'	'	'
Assets measured at fair value	'	'	'
Unrealized gain (loss) on investments	0	500,000	'
Recurring basis	'	'	'
Assets measured at fair value	'	'	'
Cash and cash equivalents	90,782,000	'	113,894,000
Certificate of deposit	2,153,000	'	'
Total assets measured at fair value	92,935,000	'	113,894,000
Recurring basis | Level 1	'	'	'
Assets measured at fair value	'	'	'
Cash and cash equivalents	90,782,000	'	113,894,000
Certificate of deposit	2,153,000	'	'
Total assets measured at fair value	$92,935,000	'	$113,894,000

Summary_of_Significant_Account5

Summary of Significant Accounting Policies (Details 3) (USD $)	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2011	Dec. 31, 2011
In Millions, unless otherwise specified		Premacure License Agreement	Ipsen and Genentech License Agreement	Eleison License Agreement
License and Collaborative Agreements	'	'	'	'
License revenues	'	$11.50	$3.40	$1
Income Taxes	'	'	'	'
Uncertain tax positions	$0	'	'	'

Summary_of_Significant_Account6

Summary of Significant Accounting Policies (Details 4) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerator:	'	'	'	'	'	'	'	'	'	'	'
Net loss attributable to common stockholders	'	'	'	'	'	'	'	'	($56,073)	($41,374)	($68,839)
Denominator:	'	'	'	'	'	'	'	'	'	'	'
Weighted average common shares used in calculation of basic net loss per share:	'	'	'	'	'	'	'	'	34,980	26,545	23,348
Weighted average common shares outstanding used in calculation of diluted net loss per share	'	'	'	'	'	'	'	'	34,980	26,545	23,348
Net loss per share:	'	'	'	'	'	'	'	'	'	'	'
Basic and Diluted (in dollars per share)	($0.41)	($0.46)	($0.28)	($0.43)	($0.49)	($0.38)	($0.39)	($0.28)	($1.60)	($1.56)	($2.95)

Summary_of_Significant_Account7

Summary of Significant Accounting Policies (Details 5)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Information	'	'	'
Number of reportable segments	1	'	'
Warrant 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 (in shares)	'	330	158
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 (in shares)	3,633	1,818	892
Restricted stock and restricted stock units	'	'	'
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 (in shares)	93	216	487

Beneficial_Conversion_Charge_B1

Beneficial Conversion Charge ("BCC") (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2011
Beneficial Conversion Charge ("BCC")	'
Non-cash BCC recorded	$9.20
Discount on fair value of common stock (in dollars per share)	$1

Accrued_Expenses_Details

Accrued Expenses (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accrued Expenses	'	'
Accrued clinical trial expenses	$2,484	$1,460
Accrued technical operation expenses	1,220	'
Liability for stock-based compensation awards	'	1,204
Accrued professional fees	24	185
Accrued interest payable	159	80
Other accrued expenses	18	4
Total accrued expenses	$3,905	$2,933

Identifiable_Intangible_Assets1

Identifiable Intangible Assets and Goodwill (Details) (USD $)	12 Months Ended
	Dec. 31, 2011
Identifiable Intangible Assets and Goodwill	'
Non-cash impairment loss	$25,990,000
Impairment of in-process research and development	19,700,000
Goodwill impairment loss	$6,300,000

Fixed_Assets_net_Details

Fixed Assets, net (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment	'	'	'
Fixed assets, gross	$5,374,000	$4,548,000	'
Less accumulated depreciation and amortization	-3,562,000	-2,882,000	'
Fixed assets, net	1,812,000	1,666,000	'
Depreciation and amortization	680,000	561,000	343,000
Net carrying value of capital lease obligations	100,000	300,000	'
Lab equipment	'	'	'
Property, Plant and Equipment	'	'	'
Fixed assets, gross	3,371,000	2,872,000	'
Estimated Useful Life	'7 years	'	'
Furniture and fixtures	'	'	'
Property, Plant and Equipment	'	'	'
Fixed assets, gross	65,000	65,000	'
Estimated Useful Life	'7 years	'	'
Computer hardware and software	'	'	'
Property, Plant and Equipment	'	'	'
Fixed assets, gross	718,000	588,000	'
Computer hardware and software | Minimum	'	'	'
Property, Plant and Equipment	'	'	'
Estimated Useful Life	'3 years	'	'
Computer hardware and software | Maximum	'	'	'
Property, Plant and Equipment	'	'	'
Estimated Useful Life	'5 years	'	'
Office equipment	'	'	'
Property, Plant and Equipment	'	'	'
Fixed assets, gross	117,000	117,000	'
Estimated Useful Life	'7 years	'	'
Manufacturing Equipment	'	'	'
Property, Plant and Equipment	'	'	'
Fixed assets, gross	375,000	325,000	'
Estimated Useful Life	'7 years	'	'
Leasehold improvements	'	'	'
Property, Plant and Equipment	'	'	'
Fixed assets, gross	612,000	581,000	'
Construction in Progress (CIP)	'	'	'
Property, Plant and Equipment	'	'	'
Fixed assets, gross	$116,000	'	'

Debt_Details

Debt (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Jun. 29, 2012	Dec. 31, 2013	Dec. 31, 2013	Jun. 29, 2012	Dec. 27, 2012
			Loan and Security Agreement	Loan and Security Agreement	Notes	Note A	Note B
			item
Debt	'	'	'	'	'	'	'
Maximum borrowing capacity of term loan	'	'	$20,000,000	'	'	'	'
Incremental amount of term loan	'	'	'	'	'	10,000,000	10,000,000
Number of Secured Promissory Notes	'	'	2	'	'	'	'
Interest rate (as a percent)	'	'	'	'	9.25%	'	'
Period over which note is to be repaid	'	'	'	'	'	'42 months	'36 months
Payment periods representing interest only	'	'	'	'	'	'12 months	'6 months
Periods of equal payment of principal and interest	'	'	'	'	'	'30 months	'30 months
Period over which principal payment could be delayed	'	'	'	'5 months	'	'	'
Fee to be paid to extend the interest-only period	'	'	'	100,000	'	'	'
"End of term" charge	'	'	390,000	'	'	'	'
Additional interest rate in event of default (as a percent)	'	'	'	5.00%	'	'	'
Limit on lender's participation rights in certain future private equity financings	'	'	'	1,000,000	'	'	'
Debt:	'	'	'	'	'	'	'
Notes payable	20,000,000	'	'	'	'	'	'
Accretion of end of term charge	204,000	'	'	'	'	'	'
Issuance fees paid to lender	-215,000	'	'	'	'	'	'
Discount from warrant	-368,000	'	'	'	'	'	'
Current portion of long-term debt	-3,283,000	'	'	'	'	'	'
Long-term debt	16,338,000	16,221,000	'	'	'	'	'
Future principal repayments of the Notes	'	'	'	'	'	'	'
2014	3,626,000	'	'	'	'	'	'
2015	7,785,000	'	'	'	'	'	'
2016	8,589,000	'	'	'	'	'	'
Total	$20,000,000	'	'	'	'	'	'

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)	0 Months Ended		12 Months Ended		0 Months Ended					12 Months Ended
	Jul. 22, 2013	Sep. 28, 2012	Dec. 31, 2013	Dec. 31, 2012	2-May-13	Dec. 31, 2013	Jun. 29, 2012	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
					Warrant	Warrant	Warrant	Stock options	Restricted stock units	Common Stock
Stockholders' Equity	'	'	'	'	'	'	'	'	'	'
Common stock, authorized shares	'	'	500,000,000	500,000,000	'	'	'	'	'	'
Common stock, par value (in dollars per share)	'	'	$0.01	$0.01	'	'	'	'	'	'
Common stock, issued shares	'	'	39,137,679	31,488,204	'	'	'	'	'	'
Common stock, outstanding shares	'	'	39,137,679	31,488,204	'	'	'	'	'	'
Common stock disclosures	'	'	'	'	'	'	'	'	'	'
Holdback shares retained as security for indemnification payments	'	'	'	'	'	'	'	'	'	1,765,271
Common stock shares reserved for issuance	'	'	'	'	'	'	'	3,632,996	92,641	'
Number of shares issued under underwritten public offering	6,900,000	6,304,102	'	'	'	'	'	'	'	'
Number of share's exercise in full of over-allotment option by underwriter	900,000	'	'	'	'	'	'	'	'	'
Shares price (in dollars per share)	$10.40	$4.07	'	'	'	'	'	'	'	'
Net proceeds from the sale of shares	$67,000,000	$25,700,000	$67,017,000	$25,658,000	'	'	'	'	'	'
Underwriter's discount and offering expenses	4,700,000	'	'	'	'	'	'	'	'	'
Warrant disclosures	'	'	'	'	'	'	'	'	'	'
Warrant to purchase common stock, number of shares	'	'	'	'	'	0	329,932	'	'	'
Exercise price of warrants (in dollars per share)	'	'	'	'	'	'	$2.94	'	'	'
Fair value of warrant	'	'	'	'	$800,000	'	'	'	'	'
Warrant Shares issued and delivered	'	'	'	'	223,431	'	'	'	'	'
Warrant Shares outstanding	'	'	'	'	'	0	'	'	'	'

StockBased_Compensation_Detail

Stock-Based Compensation (Details)	Dec. 31, 2013	Mar. 15, 2013	Mar. 31, 2013	Dec. 31, 2013	Oct. 31, 2013
	item	2000 Stock Incentive Plan	2000 Stock Incentive Plan	2013 Incentive Plan	Stock Purchase Plan
Stock Based Compensation disclosures	'	'	'	'	'
Number of equity compensation plans	3	'	'	'	'
Annual sublimit for stock options, performance shares (including RSUs) and shares of restricted stock issued to a single employee	'	1,500,000	'	1,500,000	'
Purchase price per share as a percentage of fair market value of the shares on the purchase date	'	'	'	'	85.00%
Shares of common stock, maximum authorized for issuance	'	'	'	3,053,833	'
Shares available for grant	'	'	'	1,811,064	'
RSUs and stock options in excess of the per person annual sub-limits	'	'	1,400,000	'	'

StockBased_Compensation_Detail1

Stock-Based Compensation (Details 2) (USD $)	0 Months Ended	12 Months Ended
	Apr. 02, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock Option disclosures	'	'	'	'
Granted (in shares)	'	2,323,500	1,116,384	766,000
Number of Shares	'	'	'	'
Options outstanding (in shares)	'	1,817,839	891,751	214,275
Granted (in shares)	'	2,323,500	1,116,384	766,000
Exercised (in shares)	'	-371,743	-30,250	-5,200
Forfeited and expired (in shares)	'	-136,600	-160,046	-83,324
Options outstanding (in shares)	'	3,632,996	1,817,839	891,751
Vested and expected to vest (in shares)	'	3,402,306	1,692,915	816,414
Exercisable (in shares)	'	484,213	438,145	125,751
Weighted Average Exercise Price	'	'	'	'
Options outstanding (in dollars per share)	'	$4.10	$5.15	$18.43
Granted (in dollars per share)	'	$10.53	$4.12	$3.77
Exercised (in dollars per share)	'	$4.37	$7.08	$6.16
Forfeited and expired (in dollars per share)	'	$10.49	$9.54	$26.57
Options outstanding (in dollars per share)	'	$7.94	$4.10	$5.15
Vested and expected to vest (in dollars per share)	'	$7.88	$4.11	$5.30
Exercisable (in dollars per share)	'	$4.25	$4.59	$13.54
Weighted Average Remaining Contractual Life	'	'	'	'
Options outstanding	'	'8 years 11 months 5 days	'	'
Vested and expected to vest	'	'8 years 10 months 28 days	'	'
Exercisable	'	'7 years 4 months 10 days	'	'
Aggregate Intrinsic Value	'	'	'	'
Options outstanding (in dollars)	'	$32,903,657	'	'
Vested and expected to vest (in dollars)	'	31,012,054	'	'
Exercisable (in dollars)	'	$6,176,106	'	'
Stock options	'	'	'	'
Stock Option disclosures	'	'	'	'
Granted (in shares)	300,000	'	'	'
Fair value and assumptions used in determining fair value of stock options	'	'	'	'
Dividend yield (as a percent)	'	0.00%	0.00%	0.00%
Expected option term	'	'6 years 3 months	'6 years 3 months	'6 years 3 months
Weighted-average fair value of stock options granted (in dollars per share)	'	$8.16	$3.21	$2.68
Number of Shares	'	'	'	'
Granted (in shares)	300,000	'	'	'
Stock options | Minimum	'	'	'	'
Fair value and assumptions used in determining fair value of stock options	'	'	'	'
Volatility (as a percent)	'	86.20%	99.10%	111.60%
Risk-free interest rate (as a percent)	'	0.65%	0.57%	0.91%
Stock options | Maximum	'	'	'	'
Fair value and assumptions used in determining fair value of stock options	'	'	'	'
Volatility (as a percent)	'	96.00%	107.10%	128.70%
Risk-free interest rate (as a percent)	'	1.65%	0.99%	2.12%

StockBased_Compensation_Detail2

Stock-Based Compensation (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock options	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range	'	'	'
Total intrinsic value of stock options exercised during the period	$2,700,000	$25,000	$23,000
Unrecognized compensation expense related to unvested stock options	$23,500,000	'	'
Expected weighted average period for recognizing unrecognized compensation expense	'2 years 7 months 20 days	'	'
$3.03 to $3.29	'	'	'
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)	$3.29	'	'
Number of Options outstanding (in shares)	296,687	'	'
Weighted Average Remaining Contractual Term	'7 years 5 months 16 days	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$3.04	'	'
Number of Options exercisable (in shares)	153,089	'	'
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$3.04	'	'
$3.40 to $3.40	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range	'	'	'
Range of Exercise Prices lower range limit (in dollars per share)	$3.40	'	'
Range of Exercise Prices upper range limit (in dollars per share)	$3.40	'	'
Number of Options outstanding (in shares)	708,314	'	'
Weighted Average Remaining Contractual Term	'8 years 8 months 8 days	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$3.40	'	'
Number of Options exercisable (in shares)	177,079	'	'
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$3.40	'	'
$3.48 to $6.65	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range	'	'	'
Range of Exercise Prices lower range limit (in dollars per share)	$3.48	'	'
Range of Exercise Prices upper range limit (in dollars per share)	$6.65	'	'
Number of Options outstanding (in shares)	423,595	'	'
Weighted Average Remaining Contractual Term	'8 years 4 months 28 days	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$5.55	'	'
Number of Options exercisable (in shares)	125,045	'	'
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$5.64	'	'
$6.70 to $6.70	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range	'	'	'
Range of Exercise Prices lower range limit (in dollars per share)	$6.70	'	'
Range of Exercise Prices upper range limit (in dollars per share)	$6.70	'	'
Number of Options outstanding (in shares)	20,000	'	'
Weighted Average Remaining Contractual Term	'9 years 14 days	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$6.70	'	'
$6.90 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)	$6.90	'	'
Range of Exercise Prices upper range limit (in dollars per share)	$6.90	'	'
Number of Options outstanding (in shares)	381,200	'	'
Weighted Average Remaining Contractual Term	'8 years 11 months 23 days	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$6.90	'	'
Number of Options exercisable (in shares)	10,000	'	'
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$6.90	'	'
$6.96 to $7.44	'	'	'
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)	$7.44	'	'
Number of Options outstanding (in shares)	109,500	'	'
Weighted Average Remaining Contractual Term	'9 years 7 days	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$6.99	'	'
$7.45 to $7.45	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range	'	'	'
Range of Exercise Prices lower range limit (in dollars per share)	$7.45	'	'
Range of Exercise Prices upper range limit (in dollars per share)	$7.45	'	'
Number of Options outstanding (in shares)	375,000	'	'
Weighted Average Remaining Contractual Term	'9 years 3 months	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$7.45	'	'
$8.30 to $11.46	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range	'	'	'
Range of Exercise Prices lower range limit (in dollars per share)	$8.30	'	'
Range of Exercise Prices upper range limit (in dollars per share)	$11.46	'	'
Number of Options outstanding (in shares)	312,950	'	'
Weighted Average Remaining Contractual Term	'9 years 5 months 1 day	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$10.96	'	'
Number of Options exercisable (in shares)	5,250	'	'
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$8.30	'	'
$12.44 to $12.44	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range	'	'	'
Range of Exercise Prices lower range limit (in dollars per share)	$12.44	'	'
Range of Exercise Prices upper range limit (in dollars per share)	$12.44	'	'
Number of Options outstanding (in shares)	565,050	'	'
Weighted Average Remaining Contractual Term	'9 years 1 month 28 days	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$12.44	'	'
Number of Options exercisable (in shares)	13,750	'	'
Exercisable Options, Weighted Average Exercise Price (in dollars per share)	$12.44	'	'
$12.78 to $16.54	'	'	'
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range	'	'	'
Range of Exercise Prices lower range limit (in dollars per share)	$12.78	'	'
Range of Exercise Prices upper range limit (in dollars per share)	$16.54	'	'
Number of Options outstanding (in shares)	440,700	'	'
Weighted Average Remaining Contractual Term	'9 years 9 months 18 days	'	'
Outstanding Options, Weighted Average Exercise Price (in dollars per share)	$14.55	'	'

StockBased_Compensation_Detail3

Stock-Based Compensation (Details 4) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock options and RSUs	'	'	'
Weighted Average Grant Price	'	'	'
Allocated share-based compensation expense	$8.70	$3	$1.60
Stock options and RSUs | Research and development expenses	'	'	'
Weighted Average Grant Price	'	'	'
Allocated share-based compensation expense	2.4	0.7	0.5
Stock options and RSUs | General and administrative expenses	'	'	'
Weighted Average Grant Price	'	'	'
Allocated share-based compensation expense	6.3	2.3	1.1
Restricted stock units	'	'	'
Number of RSUs	'	'	'
Outstanding, beginning balance (in shares)	215,525	487,025	'
Granted (in shares)	55,317	61,011	491,255
Released (in shares)	-177,316	-322,819	'
Forfeited (in shares)	-885	-9,692	-4,230
Outstanding, ending balance (in shares)	92,641	215,525	487,025
Expected to Vest (in shares)	92,641	'	'
Weighted Average Grant Price	'	'	'
Outstanding weighted average grant price (in dollars per share)	$6.26	$6.37	'
Granted (in dollars per share)	$6.77	$3.44	$6.36
Released (in dollars per share)	$6.42	$4.59	'
Forfeited (in dollars per share)	$5	$5.69	$5.13
Outstanding weighted average grant price (in dollars per share)	$6.27	$6.26	$6.37
Expected to Vest (in dollars per share)	$6.27	'	'
Stock-based compensation expense that resulted from the remeasurement of awards	0.8	'	'
Stock options	'	'	'
Weighted Average Grant Price	'	'	'
Stock-based compensation expense that resulted from the remeasurement of awards	$3.30	'	'
Restricted Stock and Restricted Stock Units	'	'	'
Stock Based Compensation disclosures	'	'	'
Number of common shares each award holder is entitled to receive	1	'	'
Requisite service period	'3 years	'	'

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes	'	'	'
Benefit from income taxes	$1,221,000	$0	$0
Effective tax rate (as a percent)	2.00%	0.00%	0.00%
NOL carryforwards	'	'	'
Increase in valuation allowance	28,000,000	'	'
Unrecognized tax benefits disclosures	'	'	'
Unrecognized tax benefits, reserves	0	0	'
Unrecognized tax benefits, interest and penalties accrued	0	0	'
Differences between the U.S. federal statutory tax rate and effective tax rate	'	'	'
Statutory federal tax rate (as a percent)	34.00%	34.00%	34.00%
Permanent items (as a percent)	'	'	-4.00%
State income taxes net of federal benefit (as a percent)	7.00%	4.00%	3.00%
Research and development credit (as a percent)	7.00%	1.00%	5.00%
Expired net operating loss carryforwards (as a percent)	'	-15.00%	-10.00%
Change in state tax rate (as a percent)	2.00%	'	'
Change in valuation allowance (as a percent)	-49.00%	-22.00%	-27.00%
Other (as a percent)	1.00%	-2.00%	-1.00%
Effective tax rate (as a percent)	2.00%	0.00%	0.00%
Deferred tax assets	'	'	'
Net operating loss carryforwards	149,753,000	128,257,000	'
General business credits	15,209,000	10,501,000	'
Alternative Minimum Tax (AMT) credit	418,000	418,000	'
Other	5,951,000	3,007,000	'
Gross deferred tax assets	171,331,000	142,183,000	'
Deferred tax liabilities	'	'	'
In-process research and development	-23,245,000	-22,093,000	'
Deferred tax liabilities	-23,245,000	-22,093,000	'
Net deferred tax assets	148,086,000	120,090,000	'
Valuation allowance	-148,086,000	-120,090,000	'
IRS	'	'	'
NOL carryforwards	'	'	'
Net operating loss carryforwards for income tax purposes	398,700,000	'	'
Ownership change, as defined in Section 382, which could limit utilization of NOLs (as a percent)	50.00%	'	'
Period of time for measuring ownership changes under Section 382	'3 years	'	'
New Jersey	'	'	'
NOL carryforwards	'	'	'
State NOLs sold under the State of New Jersey's Technology Business Tax Certificate Transfer Program	27,000,000	'	'
Cash proceeds from sale of NOLs, net of commissions	$1,200,000	'	'

License_and_Collaboration_Agre1

License and Collaboration Agreements (Details) (USD $)	12 Months Ended		1 Months Ended	12 Months Ended		12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2011	Mar. 31, 2013	Dec. 31, 2013	Apr. 29, 2013	Dec. 31, 2013	Dec. 31, 2009	Dec. 31, 2005
	TriAct License Agreement	Eleison License Agreement	Premacure License Agreement	Premacure License Agreement	Premacure License Agreement	CFFT	CFFT	CFFT
License and Collaborative Agreements	'	'	'	'	'	'	'	'
Number of shares received	0	'	'	'	'	'	'	'
License revenues	'	$1	'	$11.50	'	'	'	'
License purchase option price	'	'	11.5	'	'	'	'	'
Proceeds from sale of license	'	'	'	'	11.5	'	'	'
Compensation earned under research funding agreements with CFFT	'	'	'	'	'	'	2.2	1.7
Royalty payable on approval of ARIKAYCE as commercialized drug	'	'	'	'	'	13.4	'	'
Royalty payment period	'	'	'	'	'	'3 years	'	'
Period for meeting sales milestones for additional royalty payments	'	'	'	'	'	'5 years	'	'
Royalty payable on meeting certain sales milestones	'	'	'	'	'	$3.90	'	'

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Commitments	'	'	'
Future minimum rental payments under leases	$4,489,000	'	'
Rent expense charged to operations	1,000,000	1,000,000	1,000,000
Future minimum rental payments under operating leases	'	'	'
2014	1,237,000	'	'
2015	944,000	'	'
2016	886,000	'	'
2017	474,000	'	'
2018	488,000	'	'
2019	460,000	'	'
Total	4,489,000	'	'
Monmouth Junction New Jersey Facility	'	'	'
Commitments	'	'	'
Number of Leases	2	'	'
Future minimum rental payments under leases	700,000	'	'
Future minimum rental payments under operating leases	'	'	'
Total	700,000	'	'
Bridgewater New Jersey Facility	'	'	'
Commitments	'	'	'
Number of Leases	2	'	'
Future minimum rental payments under leases	2,400,000	'	'
Future minimum rental payments under operating leases	'	'	'
Total	2,400,000	'	'
Richmond facility	'	'	'
Commitments	'	'	'
Future minimum rental payments under leases	1,400,000	'	'
Net present value charge	'	'	1,200,000
Remaining rental accrual	700,000	'	'
Future minimum rental payments under operating leases	'	'	'
Total	$1,400,000	'	'

Commitments_and_Contingencies_2

Commitments and Contingencies (Details 2)	0 Months Ended		12 Months Ended
	Jun. 29, 2011	Aug. 01, 2012	Dec. 31, 2013
	Cacchillo v. Insmed	Cacchillo v. Insmed	Pilkiewicz v. Transave LLC
	item	item
Legal Proceedings	'	'	'
Number of claims dismissed	6	'	'
Claims remaining	'	3	'
Number of dissenting shares to Transave Merger represented in appraisal action	'	'	7,770,000
Total holdback shares as securities for indemnification payments due under merger agreement	'	'	1,765,271

Quarterly_Financial_Data_Unaud2

Quarterly Financial Data (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Data (Unaudited)	'	'	'	'	'	'	'	'	'	'	'
Revenues	'	'	$11,500	'	'	'	'	'	$11,500	'	$4,417
Operating loss	-15,594	-16,842	-8,270	-14,309	-15,838	-9,353	-9,983	-7,264	-55,015	-42,438	-61,719
Net loss	($16,214)	($17,327)	($8,854)	($13,678)	($15,451)	($9,382)	($9,696)	($6,845)	($56,073)	($41,374)	($59,664)
Basic and diluted net loss attributable to common stockholders per share (in dollars per share)	($0.41)	($0.46)	($0.28)	($0.43)	($0.49)	($0.38)	($0.39)	($0.28)	($1.60)	($1.56)	($2.95)

Retirement_Plan_Details

Retirement Plan (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Retirement Plan	'	'	'
Employer contribution to retirement plan	$0	$0	$0

Subsequent_Events_Details

Subsequent Events (Details) (Subsequent events, Agreement with Therapure Biopharma Inc.)	0 Months Ended
	Feb. 10, 2014
Subsequent events | Agreement with Therapure Biopharma Inc.	'
Subsequent Events	'
Initial term of collaborative arrangement	'5 years
Successive renewal period of collaborative arrangement	'2 years
Prior written notice period for termination	'2 years
Minimum number of days of advance notice for termination	'180 days