Accounting Policies, by Policy (Policies)	9 Months Ended
Sep. 30, 2014
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	Basis of Presentation All significant intercompany activity has been eliminated in the preparation of the condensed consolidated financial statements. The unaudited condensed consolidated financial statements have been prepared in accordance with the requirements of Form 10-Q and Rule 10-01 of Regulation S-X. Some information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles, or GAAP, have been condensed or omitted pursuant to those rules and regulations. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the consolidated financial position, results of operations, and cash flows of the Company. The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries: International Medication Systems, Limited, or IMS; Amphastar Laboratories, Inc.; Armstrong Pharmaceuticals, Inc., or Armstrong; Amphastar Nanjing Pharmaceuticals Co., Ltd., or ANP; and Amphastar France Pharmaceuticals, S.A.S., or AFP.
Reclassification, Policy [Policy Text Block]	Amounts reclassified Certain amounts in the prior years’ financial statements have been reclassified to conform to the current year presentation. These reclassifications relate to the Company’s accounting for accrued chargebacks, which was originally included on the Company’s consolidated balance sheets as a liability and is now reflected as a reduction to accounts receivable. These reclassifications have no impact on net income or cash flows.
Use of Estimates, Policy [Policy Text Block]	Use of Estimates The preparation of consolidated financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The principal accounting estimates include: determination of allowances for doubtful accounts and discounts, liabilities for product returns and chargebacks, reserves for excess or unsellable inventory, impairment of long-lived and intangible assets and goodwill, self-insured claims, workers’ compensation liabilities, litigation reserves, stock price volatilities for share-based compensation expense, fair market values of the Company’s common stock, valuation allowances for deferred tax assets, and liabilities for uncertain income tax positions.
Foreign Currency Transactions and Translations Policy [Policy Text Block]	Foreign Currency The functional currency of the Company and its domestic and Chinese subsidiaries is the U.S. dollar, or USD. The Company’s Chinese subsidiary, ANP, maintains its books of record in Chinese Yuan. These books are remeasured into the functional currency of USD using the current or historical exchange rates. The resulting currency remeasurement adjustments and other transactional foreign exchange gains and losses are reflected in the Company’s statement of operations. The Company’s French subsidiary, AFP, maintains its books of record in Euros, which is the local currency in France and has been determined to be its functional currency. These books are translated to USD at the average exchange rates during the period. Assets and liabilities are translated at the rate of exchange prevailing on the balance sheet date. Equity is translated at the prevailing rate of exchange at the date of the equity transactions. Translation adjustments are reflected in stockholders’ equity and are included as a component of other comprehensive income (loss). Additionally, the Company does not undertake hedging transactions to cover its foreign currency exposure.
Comprehensive Income, Policy [Policy Text Block]	Comprehensive Income (Loss) For the three and nine months ended September 30, 2014, the Company includes its foreign currency translation adjustment as part of its comprehensive loss as a result of establishing the Company’s subsidiary, AFP, in France. For the three and nine months ended September 30, 2013, net income (loss) equaled total comprehensive income (loss).
Fair Value of Financial Instruments, Policy [Policy Text Block]	Financial Instruments The carrying amounts of cash and cash equivalents, short-term investments, accounts receivable, accounts payable, accrued expenses, and short-term borrowings approximate fair value due to the short maturity of these items. A majority of the Company’s long-term obligations consist of variable rate debt and their carrying value approximates fair value. Their carrying value approximates fair value as the stated borrowing rates are comparable to rates currently offered to the Company for instruments with similar maturities. However, the Company has one fixed-rate, long-term mortgage for which the carrying value differs from the fair value and is not remeasured on a recurring basis (see Note 13).
Income Tax, Policy [Policy Text Block]	Deferred Income Taxes The Company utilizes the liability method of accounting for income taxes. Under the liability method, deferred taxes are determined based on the temporary differences between the financial statements and the tax basis of assets and liabilities using enacted tax rates. A valuation allowance is recorded when it is more likely than not that the deferred tax assets will not be realized. The Company has adopted the with-and-without methodology for determining when excess tax benefits from the exercise of share-based awards are realized. Under the with-and-without methodology, current year operating loss deductions and prior-year operating loss carryforwards are deemed to be utilized prior to the utilization of current-year excess tax benefits from share-based awards.
Business Combinations Policy [Policy Text Block]	Business Combinations Business combinations are accounted for in accordance with Accounting Standards Codification, or ASC 805, Business Combinations, using the acquisition method of accounting. The acquisition method of accounting requires an acquirer to recognize the assets acquired and the liabilities assumed at the acquisition date measured at their fair values as of that date. Fair value determinations are based on discounted cash flow analyses or other valuation techniques. In determining the fair value of the assets acquired and liabilities assumed in a material acquisition, the Company may utilize appraisals from third party valuation firms to determine fair values of some or all of the assets acquired and liabilities assumed, or may complete some or all of the valuations internally. In either case, the Company takes full responsibility for the determination of the fair value of the assets acquired and liabilities assumed. The value of goodwill reflects the excess of the fair value of the consideration conveyed to the seller over the fair value of the net assets received. Under the acquisition method of accounting, the Company will identify the acquirer and the closing date and apply applicable recognition principles and conditions. Acquisition-related costs are costs the Company incurs to effect a business combination. The Company accounts for acquisition-related costs as expenses in the periods in which the costs are incurred.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements In July 2013, the Financial Accounting Standards Board, or FASB, issued an Accounting Standard Update to the accounting guidance to address the diversity in practice related to the financial statement presentation of unrecognized tax benefits as either a reduction of a deferred tax asset or a liability when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. This guidance is effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2013. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. In April 2014, the FASB issued an accounting standards update that raises the threshold for disposals to qualify as discontinued operations and allows companies to have significant continuing involvement with and continuing cash flows from or to the discontinued operation. It also requires additional disclosures for discontinued operations and new disclosures for individually material disposal transactions that do not meet the definition of a discontinued operation. This guidance will be effective for fiscal years beginning after December 15, 2014, which will be the Company's fiscal year 2015, with early adoption permitted. The Company does not expect the adoption of the guidance will have a material impact on the Company's consolidated financial statements. In May 2014, the FASB issued an accounting standards update that creates a single source of revenue guidance for companies in all industries. The new standard provides guidance for all revenue arising from contracts with customers and affects all entities that enter into contracts to provide goods or services to their customers, unless the contracts are within the scope of other accounting standards. It also provides a model for the measurement and recognition of gains and losses on the sale of certain nonfinancial assets. This guidance must be adopted using either a full retrospective approach for all periods presented or a modified retrospective approach and will be effective for fiscal years beginning after December 15, 2016, which will be the Company's fiscal year 2017. The Company has not yet evaluated the potential impact of adopting the guidance on the Company's consolidated financial statements. In June 2014, the FASB issued an accounting standards update that requires a performance target that affects vesting of a share-based payment award and that could be achieved after the requisite service period to be treated as a performance condition. As such, the performance target should not be reflected in estimating the grant-date fair value of the award. Compensation cost should be recognized over the required service period, if it is probable that the performance target will be achieved. This guidance will be effective for fiscal years beginning after December 15, 2015, which will be the Company's fiscal year 2016, with early adoption permitted. The Company does not expect the adoption of the guidance will have a material impact on the Company's consolidated financial statements. In August 2014, the FASB issued an accounting standards update that will require management to evaluate if there is substantial doubt about the Company’s ability to continue as a going concern and, if so, to disclose this in both interim and annual reporting periods. This guidance will become effective for the Company’s annual filing for the period ending December 31, 2016 and interim periods thereafter, and allows for early adoption. The Company does not expect the adoption of the guidance will have a material impact on the Company’s consolidated financial statements.

Accounting Policies, by Policy (Policies)

9 Months Ended

Sep. 30, 2014

Basis of Accounting, Policy [Policy Text Block]

Basis of Presentation

All significant intercompany activity has been eliminated in the preparation of the condensed consolidated financial statements. The unaudited condensed consolidated financial statements have been prepared in accordance with the requirements of Form 10-Q and Rule 10-01 of Regulation S-X. Some information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles, or GAAP, have been condensed or omitted pursuant to those rules and regulations. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the consolidated financial position, results of operations, and cash flows of the Company.

The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries: International Medication Systems, Limited, or IMS; Amphastar Laboratories, Inc.; Armstrong Pharmaceuticals, Inc., or Armstrong; Amphastar Nanjing Pharmaceuticals Co., Ltd., or ANP; and Amphastar France Pharmaceuticals, S.A.S., or AFP.

Reclassification, Policy [Policy Text Block]

Amounts reclassified

Certain amounts in the prior years’ financial statements have been reclassified to conform to the current year presentation. These reclassifications relate to the Company’s accounting for accrued chargebacks, which was originally included on the Company’s consolidated balance sheets as a liability and is now reflected as a reduction to accounts receivable. These reclassifications have no impact on net income or cash flows.

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

The preparation of consolidated financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The principal accounting estimates include: determination of allowances for doubtful accounts and discounts, liabilities for product returns and chargebacks, reserves for excess or unsellable inventory, impairment of long-lived and intangible assets and goodwill, self-insured claims, workers’ compensation liabilities, litigation reserves, stock price volatilities for share-based compensation expense, fair market values of the Company’s common stock, valuation allowances for deferred tax assets, and liabilities for uncertain income tax positions.

Foreign Currency Transactions and Translations Policy [Policy Text Block]

Foreign Currency

The functional currency of the Company and its domestic and Chinese subsidiaries is the U.S. dollar, or USD. The Company’s Chinese subsidiary, ANP, maintains its books of record in Chinese Yuan. These books are remeasured into the functional currency of USD using the current or historical exchange rates. The resulting currency remeasurement adjustments and other transactional foreign exchange gains and losses are reflected in the Company’s statement of operations. The Company’s French subsidiary, AFP, maintains its books of record in Euros, which is the local currency in France and has been determined to be its functional currency. These books are translated to USD at the average exchange rates during the period. Assets and liabilities are translated at the rate of exchange prevailing on the balance sheet date. Equity is translated at the prevailing rate of exchange at the date of the equity transactions. Translation adjustments are reflected in stockholders’ equity and are included as a component of other comprehensive income (loss). Additionally, the Company does not undertake hedging transactions to cover its foreign currency exposure.

Comprehensive Income, Policy [Policy Text Block]

Comprehensive Income (Loss)

For the three and nine months ended September 30, 2014, the Company includes its foreign currency translation adjustment as part of its comprehensive loss as a result of establishing the Company’s subsidiary, AFP, in France. For the three and nine months ended September 30, 2013, net income (loss) equaled total comprehensive income (loss).

Fair Value of Financial Instruments, Policy [Policy Text Block]

Financial Instruments

The carrying amounts of cash and cash equivalents, short-term investments, accounts receivable, accounts payable, accrued expenses, and short-term borrowings approximate fair value due to the short maturity of these items. A majority of the Company’s long-term obligations consist of variable rate debt and their carrying value approximates fair value. Their carrying value approximates fair value as the stated borrowing rates are comparable to rates currently offered to the Company for instruments with similar maturities. However, the Company has one fixed-rate, long-term mortgage for which the carrying value differs from the fair value and is not remeasured on a recurring basis (see Note 13).

Income Tax, Policy [Policy Text Block]

Deferred Income Taxes

The Company utilizes the liability method of accounting for income taxes. Under the liability method, deferred taxes are determined based on the temporary differences between the financial statements and the tax basis of assets and liabilities using enacted tax rates. A valuation allowance is recorded when it is more likely than not that the deferred tax assets will not be realized. The Company has adopted the with-and-without methodology for determining when excess tax benefits from the exercise of share-based awards are realized. Under the with-and-without methodology, current year operating loss deductions and prior-year operating loss carryforwards are deemed to be utilized prior to the utilization of current-year excess tax benefits from share-based awards.

Business Combinations Policy [Policy Text Block]

Business Combinations

Business combinations are accounted for in accordance with Accounting Standards Codification, or ASC 805, Business Combinations, using the acquisition method of accounting. The acquisition method of accounting requires an acquirer to recognize the assets acquired and the liabilities assumed at the acquisition date measured at their fair values as of that date. Fair value determinations are based on discounted cash flow analyses or other valuation techniques. In determining the fair value of the assets acquired and liabilities assumed in a material acquisition, the Company may utilize appraisals from third party valuation firms to determine fair values of some or all of the assets acquired and liabilities assumed, or may complete some or all of the valuations internally. In either case, the Company takes full responsibility for the determination of the fair value of the assets acquired and liabilities assumed. The value of goodwill reflects the excess of the fair value of the consideration conveyed to the seller over the fair value of the net assets received. Under the acquisition method of accounting, the Company will identify the acquirer and the closing date and apply applicable recognition principles and conditions.

Acquisition-related costs are costs the Company incurs to effect a business combination. The Company accounts for acquisition-related costs as expenses in the periods in which the costs are incurred.

New Accounting Pronouncements, Policy [Policy Text Block]

Recent Accounting Pronouncements

In July 2013, the Financial Accounting Standards Board, or FASB, issued an Accounting Standard Update to the accounting guidance to address the diversity in practice related to the financial statement presentation of unrecognized tax benefits as either a reduction of a deferred tax asset or a liability when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. This guidance is effective prospectively for fiscal years, and interim periods within those years, beginning after December 15, 2013. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements.

In April 2014, the FASB issued an accounting standards update that raises the threshold for disposals to qualify as discontinued operations and allows companies to have significant continuing involvement with and continuing cash flows from or to the discontinued operation. It also requires additional disclosures for discontinued operations and new disclosures for individually material disposal transactions that do not meet the definition of a discontinued operation. This guidance will be effective for fiscal years beginning after December 15, 2014, which will be the Company's fiscal year 2015, with early adoption permitted. The Company does not expect the adoption of the guidance will have a material impact on the Company's consolidated financial statements.

In May 2014, the FASB issued an accounting standards update that creates a single source of revenue guidance for companies in all industries. The new standard provides guidance for all revenue arising from contracts with customers and affects all entities that enter into contracts to provide goods or services to their customers, unless the contracts are within the scope of other accounting standards. It also provides a model for the measurement and recognition of gains and losses on the sale of certain nonfinancial assets. This guidance must be adopted using either a full retrospective approach for all periods presented or a modified retrospective approach and will be effective for fiscal years beginning after December 15, 2016, which will be the Company's fiscal year 2017. The Company has not yet evaluated the potential impact of adopting the guidance on the Company's consolidated financial statements.

In June 2014, the FASB issued an accounting standards update that requires a performance target that affects vesting of a share-based payment award and that could be achieved after the requisite service period to be treated as a performance condition. As such, the performance target should not be reflected in estimating the grant-date fair value of the award. Compensation cost should be recognized over the required service period, if it is probable that the performance target will be achieved. This guidance will be effective for fiscal years beginning after December 15, 2015, which will be the Company's fiscal year 2016, with early adoption permitted. The Company does not expect the adoption of the guidance will have a material impact on the Company's consolidated financial statements.

In August 2014, the FASB issued an accounting standards update that will require management to evaluate if there is substantial doubt about the Company’s ability to continue as a going concern and, if so, to disclose this in both interim and annual reporting periods. This guidance will become effective for the Company’s annual filing for the period ending December 31, 2016 and interim periods thereafter, and allows for early adoption. The Company does not expect the adoption of the guidance will have a material impact on the Company’s consolidated financial statements.