v3.19.1

Stock-Based Awards (Narrative) (Details) - USD ($)		3 Months Ended		75 Months Ended
Stock-Based Awards (Narrative) (Details) - USD ($)	Jan. 01, 2019	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from stock option exercises		$ 27,000	$ 5,000
2010 Equity Incentive Plan [Member] \| Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted				0
2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant		2,173,138		2,173,138
Stock options granted		740,146
Annual increase in shares	1,203,369
Unrecognized stock-based compensation expense for options outstanding		$ 3,780,000		$ 3,780,000
Unrecognized stock-based compensation expense, other than options		2,589,000		$ 2,589,000
2013 Plan [Member] \| Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of options exercised		9,000
Proceeds from stock option exercises		$ 27,000
Weighted average grant date fair value of options granted		$ 2.68
Unrecognized stock-based compensation expense, recognition period		2 years 11 months 16 days
2013 Plan [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value stock awards, vested, other than options		$ 1,358,000
Proceeds from the issuance of restricted stock		$ 0
Unrecognized stock-based compensation expense, recognition period		2 years 4 months 2 days

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Amount of cash inflow from issuance of shares under share-based compensation arrangement, excluding stock option exercises.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Number of additional shares authorized for issuance under an established share-based compensation plan.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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ARATANA THERAPEUTICS, INC. 10-Q