CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue:
Product revenue, net	$ 55,720us-gaap_SalesRevenueGoodsNet	$ 45,238us-gaap_SalesRevenueGoodsNet
License and collaboration revenue	49,688aria_LicenseAndCollaborationRevenue	296aria_LicenseAndCollaborationRevenue	514aria_LicenseAndCollaborationRevenue
Service revenue	4aria_ServicesRevenue	27aria_ServicesRevenue	44aria_ServicesRevenue
Total revenue	105,412us-gaap_Revenues	45,561us-gaap_Revenues	558us-gaap_Revenues
Operating expenses:
Cost of product revenue	5,224us-gaap_CostOfGoodsSold	9,612us-gaap_CostOfGoodsSold
Research and development expense	120,593us-gaap_ResearchAndDevelopmentExpense	162,900us-gaap_ResearchAndDevelopmentExpense	144,709us-gaap_ResearchAndDevelopmentExpense
Selling, general and administrative expense	139,790	146,615	60,909
Total operating expenses	265,607us-gaap_OperatingExpenses	319,127us-gaap_OperatingExpenses	205,618us-gaap_OperatingExpenses
Loss from operations	(160,195)us-gaap_OperatingIncomeLoss	(273,566)us-gaap_OperatingIncomeLoss	(205,060)us-gaap_OperatingIncomeLoss
Other income (expense):
Interest income	85us-gaap_InvestmentIncomeInterest	130us-gaap_InvestmentIncomeInterest	240us-gaap_InvestmentIncomeInterest
Interest expense	(8,075)us-gaap_InterestExpense	(153)us-gaap_InterestExpense	(199)us-gaap_InterestExpense
Gain on disposition of stock	4,768aria_GainLossOnDispositionOfStock
Revaluation of warrant liability			(15,924)
Foreign exchange gain (loss)	1,445	(130)	71
Other expense, net	(1,777)us-gaap_NonoperatingIncomeExpense	(153)us-gaap_NonoperatingIncomeExpense	(15,812)us-gaap_NonoperatingIncomeExpense
Loss before provision for income taxes	(161,972)	(273,719)	(220,872)
Provision for income taxes	630us-gaap_IncomeTaxExpenseBenefit	439us-gaap_IncomeTaxExpenseBenefit
Net loss	$ (162,602)us-gaap_NetIncomeLoss	$ (274,158)us-gaap_NetIncomeLoss	$ (220,872)us-gaap_NetIncomeLoss
Net loss per share - basic and diluted	$ (0.87)us-gaap_EarningsPerShareBasicAndDiluted	$ (1.49)us-gaap_EarningsPerShareBasicAndDiluted	$ (1.34)us-gaap_EarningsPerShareBasicAndDiluted
Weighted-average number of shares of common stock outstanding - basic and diluted	186,835	183,575	164,964

Gain (Loss) On Disposition Of Stock

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Revenue from multiple-deliverable arrangements that include licensing fees and collaboration arrangements. Licensing revenue is consideration received from another party for the right to use, but not own, certain of the entity's intangible assets. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark. Licensing fees are generally, but not always, fixed as to amount and not dependent upon the revenue generated by the licensing party. An entity may receive licensing fees for licenses that also generate royalty payments to the entity. Collaboration agreements include, but are not limited to, license fees, research and development, up-front and milestone payments.

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Services revenue which may be derived by providing other, nonspecified, services during the reporting period

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Total costs related to goods produced and sold during the reporting period.

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the cost of borrowed funds accounted for as interest expense.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

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Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense.

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The net result for the period of deducting operating expenses from operating revenues.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts.

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

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