3.25.4 html 331 574 1 false 126 0 false 10 false false R1.htm 995200090 - Document - Document And Entity Information Sheet http://www.amphastar.com/role/DocumentDocumentAndEntityInformation Document And Entity Information Cover 1 false false R2.htm 995200100 - Statement - CONSOLIDATED BALANCE SHEETS Sheet http://www.amphastar.com/role/StatementConsolidatedBalanceSheets CONSOLIDATED BALANCE SHEETS Statements 2 false false R3.htm 995200105 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical) Sheet http://www.amphastar.com/role/StatementConsolidatedBalanceSheetsParenthetical CONSOLIDATED BALANCE SHEETS (Parenthetical) Statements 3 false false R4.htm 995200200 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS Sheet http://www.amphastar.com/role/StatementConsolidatedStatementsOfOperations CONSOLIDATED STATEMENTS OF OPERATIONS Statements 4 false false R5.htm 995200300 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Sheet http://www.amphastar.com/role/StatementConsolidatedStatementsOfComprehensiveIncome CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Statements 5 false false R6.htm 995200400 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Sheet http://www.amphastar.com/role/StatementConsolidatedStatementsOfStockholdersEquity CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Statements 6 false false R7.htm 995200500 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS Sheet http://www.amphastar.com/role/StatementConsolidatedStatementsOfCashFlows CONSOLIDATED STATEMENTS OF CASH FLOWS Statements 7 false false R8.htm 995210101 - Disclosure - Business Sheet http://www.amphastar.com/role/DisclosureBusiness Business Notes 8 false false R9.htm 995210201 - Disclosure - Summary of Significant Accounting Policies Sheet http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 9 false false R10.htm 995210301 - Disclosure - Revenue Recognition Sheet http://www.amphastar.com/role/DisclosureRevenueRecognition Revenue Recognition Notes 10 false false R11.htm 995210401 - Disclosure - Net Income per Share Sheet http://www.amphastar.com/role/DisclosureNetIncomePerShare Net Income per Share Notes 11 false false R12.htm 995210501 - Disclosure - Segment Reporting Sheet http://www.amphastar.com/role/DisclosureSegmentReporting Segment Reporting Notes 12 false false R13.htm 995210601 - Disclosure - Customer and Supplier Concentration Sheet http://www.amphastar.com/role/DisclosureCustomerAndSupplierConcentration Customer and Supplier Concentration Notes 13 false false R14.htm 995210701 - Disclosure - Fair Value Measurements Sheet http://www.amphastar.com/role/DisclosureFairValueMeasurements Fair Value Measurements Notes 14 false false R15.htm 995210801 - Disclosure - Investments Sheet http://www.amphastar.com/role/DisclosureInvestments Investments Notes 15 false false R16.htm 995210901 - Disclosure - Goodwill and Intangible Assets Sheet http://www.amphastar.com/role/DisclosureGoodwillAndIntangibleAssets Goodwill and Intangible Assets Notes 16 false false R17.htm 995211001 - Disclosure - Inventories Sheet http://www.amphastar.com/role/DisclosureInventories Inventories Notes 17 false false R18.htm 995211101 - Disclosure - Property, Plant, and Equipment Sheet http://www.amphastar.com/role/DisclosurePropertyPlantAndEquipment Property, Plant, and Equipment Notes 18 false false R19.htm 995211201 - Disclosure - Accounts Payable and Accrued Liabilities Sheet http://www.amphastar.com/role/DisclosureAccountsPayableAndAccruedLiabilities Accounts Payable and Accrued Liabilities Notes 19 false false R20.htm 995211301 - Disclosure - Debt Sheet http://www.amphastar.com/role/DisclosureDebt Debt Notes 20 false false R21.htm 995211401 - Disclosure - Income Taxes Sheet http://www.amphastar.com/role/DisclosureIncomeTaxes Income Taxes Notes 21 false false R22.htm 995211501 - Disclosure - Stockholders' Equity Sheet http://www.amphastar.com/role/DisclosureStockholdersEquity Stockholders' Equity Notes 22 false false R23.htm 995211601 - Disclosure - Employee Benefits Sheet http://www.amphastar.com/role/DisclosureEmployeeBenefits Employee Benefits Notes 23 false false R24.htm 995211701 - Disclosure - Commitments and Contingencies Sheet http://www.amphastar.com/role/DisclosureCommitmentsAndContingencies Commitments and Contingencies Notes 24 false false R25.htm 995211801 - Disclosure - Related-Party Transactions Sheet http://www.amphastar.com/role/DisclosureRelatedPartyTransactions Related-Party Transactions Notes 25 false false R26.htm 995211901 - Disclosure - Litigation Sheet http://www.amphastar.com/role/DisclosureLitigation Litigation Notes 26 false false R27.htm 995212001 - Disclosure - Subsequent Events Sheet http://www.amphastar.com/role/DisclosureSubsequentEvents Subsequent Events Notes 27 false false R28.htm 995410 - Disclosure - Pay vs Performance Disclosure Sheet http://xbrl.sec.gov/ecd/role/PvpDisclosure Pay vs Performance Disclosure Notes 28 false false R29.htm 995445 - Disclosure - Insider Trading Arrangements Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements Insider Trading Arrangements Notes 29 false false R30.htm 995447 - Disclosure - Insider Trading Policies and Procedures Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc Insider Trading Policies and Procedures Notes 30 false false R31.htm 995550 - Disclosure - Cybersecurity Risk Management and Strategy Disclosure Sheet http://xbrl.sec.gov/cyd/role/CybersecurityRiskManagementAndStrategyDisclosure Cybersecurity Risk Management and Strategy Disclosure Notes 31 false false R32.htm 99920202 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPolicies 32 false false R33.htm 99930203 - Disclosure - Summary of Significant Accounting Policies (Tables) Sheet http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables Summary of Significant Accounting Policies (Tables) Tables http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPolicies 33 false false R34.htm 99930303 - Disclosure - Revenue Recognition (Tables) Sheet http://www.amphastar.com/role/DisclosureRevenueRecognitionTables Revenue Recognition (Tables) Tables http://www.amphastar.com/role/DisclosureRevenueRecognition 34 false false R35.htm 99930403 - Disclosure - Net Income per Share (Tables) Sheet http://www.amphastar.com/role/DisclosureNetIncomePerShareTables Net Income per Share (Tables) Tables http://www.amphastar.com/role/DisclosureNetIncomePerShare 35 false false R36.htm 99930503 - Disclosure - Segment Reporting (Tables) Sheet http://www.amphastar.com/role/DisclosureSegmentReportingTables Segment Reporting (Tables) Tables http://www.amphastar.com/role/DisclosureSegmentReporting 36 false false R37.htm 99930603 - Disclosure - Customer and Supplier Concentration (Tables) Sheet http://www.amphastar.com/role/DisclosureCustomerAndSupplierConcentrationTables Customer and Supplier Concentration (Tables) Tables http://www.amphastar.com/role/DisclosureCustomerAndSupplierConcentration 37 false false R38.htm 99930703 - Disclosure - Fair Value Measurements (Tables) Sheet http://www.amphastar.com/role/DisclosureFairValueMeasurementsTables Fair Value Measurements (Tables) Tables http://www.amphastar.com/role/DisclosureFairValueMeasurements 38 false false R39.htm 99930803 - Disclosure - Investments (Tables) Sheet http://www.amphastar.com/role/DisclosureInvestmentsTables Investments (Tables) Tables http://www.amphastar.com/role/DisclosureInvestments 39 false false R40.htm 99930903 - Disclosure - Goodwill and Intangible Assets (Tables) Sheet http://www.amphastar.com/role/DisclosureGoodwillAndIntangibleAssetsTables Goodwill and Intangible Assets (Tables) Tables http://www.amphastar.com/role/DisclosureGoodwillAndIntangibleAssets 40 false false R41.htm 99931003 - Disclosure - Inventories (Tables) Sheet http://www.amphastar.com/role/DisclosureInventoriesTables Inventories (Tables) Tables http://www.amphastar.com/role/DisclosureInventories 41 false false R42.htm 99931103 - Disclosure - Property, Plant, and Equipment (Tables) Sheet http://www.amphastar.com/role/DisclosurePropertyPlantAndEquipmentTables Property, Plant, and Equipment (Tables) Tables http://www.amphastar.com/role/DisclosurePropertyPlantAndEquipment 42 false false R43.htm 99931203 - Disclosure - Accounts Payable and Accrued Liabilities (Tables) Sheet http://www.amphastar.com/role/DisclosureAccountsPayableAndAccruedLiabilitiesTables Accounts Payable and Accrued Liabilities (Tables) Tables http://www.amphastar.com/role/DisclosureAccountsPayableAndAccruedLiabilities 43 false false R44.htm 99931303 - Disclosure - Debt (Tables) Sheet http://www.amphastar.com/role/DisclosureDebtTables Debt (Tables) Tables http://www.amphastar.com/role/DisclosureDebt 44 false false R45.htm 99931403 - Disclosure - Income Taxes (Tables) Sheet http://www.amphastar.com/role/DisclosureIncomeTaxesTables Income Taxes (Tables) Tables http://www.amphastar.com/role/DisclosureIncomeTaxes 45 false false R46.htm 99931503 - Disclosure - Stockholders' Equity (Tables) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquityTables Stockholders' Equity (Tables) Tables http://www.amphastar.com/role/DisclosureStockholdersEquity 46 false false R47.htm 99931703 - Disclosure - Commitments and Contingencies (Tables) Sheet http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesTables Commitments and Contingencies (Tables) Tables http://www.amphastar.com/role/DisclosureCommitmentsAndContingencies 47 false false R48.htm 99940201 - Disclosure - Summary of Significant Accounting Policies (Details) Sheet http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetails Summary of Significant Accounting Policies (Details) Details http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables 48 false false R49.htm 99940202 - Disclosure - Summary of Significant Accounting Policies (Schedule of PP&E Useful Lives) (Details) Sheet http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPoliciesScheduleOfPpEUsefulLivesDetails Summary of Significant Accounting Policies (Schedule of PP&E Useful Lives) (Details) Details http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables 49 false false R50.htm 99940203 - Disclosure - Summary of Significant Accounting Policies (Schedule of Intangible Useful Lives) (Details) Sheet http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPoliciesScheduleOfIntangibleUsefulLivesDetails Summary of Significant Accounting Policies (Schedule of Intangible Useful Lives) (Details) Details http://www.amphastar.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables 50 false false R51.htm 99940301 - Disclosure - Revenue Recognition (Analysis of the Chargeback Provision) (Details) Sheet http://www.amphastar.com/role/DisclosureRevenueRecognitionAnalysisOfChargebackProvisionDetails Revenue Recognition (Analysis of the Chargeback Provision) (Details) Details http://www.amphastar.com/role/DisclosureRevenueRecognitionTables 51 false false R52.htm 99940302 - Disclosure - Revenue Recognition (Chargebacks and Rebates Balance Sheet Accounts) (Details) Sheet http://www.amphastar.com/role/DisclosureRevenueRecognitionChargebacksAndRebatesBalanceSheetAccountsDetails Revenue Recognition (Chargebacks and Rebates Balance Sheet Accounts) (Details) Details http://www.amphastar.com/role/DisclosureRevenueRecognitionTables 52 false false R53.htm 99940303 - Disclosure - Revenue Recognition (Analysis of Product Return Liability) (Details) Sheet http://www.amphastar.com/role/DisclosureRevenueRecognitionAnalysisOfProductReturnLiabilityDetails Revenue Recognition (Analysis of Product Return Liability) (Details) Details http://www.amphastar.com/role/DisclosureRevenueRecognitionTables 53 false false R54.htm 99940401 - Disclosure - Net Income per Share (Narrative) (Details) Sheet http://www.amphastar.com/role/DisclosureNetIncomePerShareNarrativeDetails Net Income per Share (Narrative) (Details) Details http://www.amphastar.com/role/DisclosureNetIncomePerShareTables 54 false false R55.htm 99940402 - Disclosure - Net Income per Share (Calculation of Basic and Diluted Net Income (Loss) Per Share) (Details) Sheet http://www.amphastar.com/role/DisclosureNetIncomePerShareCalculationOfBasicAndDilutedNetIncomeLossPerShareDetails Net Income per Share (Calculation of Basic and Diluted Net Income (Loss) Per Share) (Details) Details http://www.amphastar.com/role/DisclosureNetIncomePerShareTables 55 false false R56.htm 99940501 - Disclosure - Segment Reporting (Selected Financial Information by Reporting Segment) (Details) Sheet http://www.amphastar.com/role/DisclosureSegmentReportingSelectedFinancialInformationByReportingSegmentDetails Segment Reporting (Selected Financial Information by Reporting Segment) (Details) Details http://www.amphastar.com/role/DisclosureSegmentReportingTables 56 false false R57.htm 99940502 - Disclosure - Segment Reporting (Summary of Net Revenues by Product) (Details) Sheet http://www.amphastar.com/role/DisclosureSegmentReportingSummaryOfNetRevenuesByProductDetails Segment Reporting (Summary of Net Revenues by Product) (Details) Details http://www.amphastar.com/role/DisclosureSegmentReportingTables 57 false false R58.htm 99940503 - Disclosure - Segment Reporting (Summary of Revenues and Long-Lived Assets by Geographic Region) (Details) Sheet http://www.amphastar.com/role/DisclosureSegmentReportingSummaryOfRevenuesAndLongLivedAssetsByGeographicRegionDetails Segment Reporting (Summary of Revenues and Long-Lived Assets by Geographic Region) (Details) Details http://www.amphastar.com/role/DisclosureSegmentReportingTables 58 false false R59.htm 99940601 - Disclosure - Customer and Supplier Concentration (Details) Sheet http://www.amphastar.com/role/DisclosureCustomerAndSupplierConcentrationDetails Customer and Supplier Concentration (Details) Details http://www.amphastar.com/role/DisclosureCustomerAndSupplierConcentrationTables 59 false false R60.htm 99940701 - Disclosure - Fair Value Measurements (Fair Values of the Company's Financial Assets and Liabilities) (Details) Sheet http://www.amphastar.com/role/DisclosureFairValueMeasurementsFairValuesOfCompanySFinancialAssetsAndLiabilitiesDetails Fair Value Measurements (Fair Values of the Company's Financial Assets and Liabilities) (Details) Details http://www.amphastar.com/role/DisclosureFairValueMeasurementsTables 60 false false R61.htm 99940801 - Disclosure - Investments (Held-to-Maturity) (Details) Sheet http://www.amphastar.com/role/DisclosureInvestmentsHeldToMaturityDetails Investments (Held-to-Maturity) (Details) Details http://www.amphastar.com/role/DisclosureInvestmentsTables 61 false false R62.htm 99940901 - Disclosure - Goodwill and Intangible Assets (Summary of Intangible Assets) (Details) Sheet http://www.amphastar.com/role/DisclosureGoodwillAndIntangibleAssetsSummaryOfIntangibleAssetsDetails Goodwill and Intangible Assets (Summary of Intangible Assets) (Details) Details http://www.amphastar.com/role/DisclosureGoodwillAndIntangibleAssetsTables 62 false false R63.htm 99940902 - Disclosure - Goodwill and Intangible Assets (Summary of Changes in the Carrying Amount of Goodwill) (Details) Sheet http://www.amphastar.com/role/DisclosureGoodwillAndIntangibleAssetsSummaryOfChangesInCarryingAmountOfGoodwillDetails Goodwill and Intangible Assets (Summary of Changes in the Carrying Amount of Goodwill) (Details) Details http://www.amphastar.com/role/DisclosureGoodwillAndIntangibleAssetsTables 63 false false R64.htm 99940903 - Disclosure - Goodwill and Intangible Assets (Summary of Expected Amortization Expense) (Details) Sheet http://www.amphastar.com/role/DisclosureGoodwillAndIntangibleAssetsSummaryOfExpectedAmortizationExpenseDetails Goodwill and Intangible Assets (Summary of Expected Amortization Expense) (Details) Details http://www.amphastar.com/role/DisclosureGoodwillAndIntangibleAssetsTables 64 false false R65.htm 99941001 - Disclosure - Inventories (Details) Sheet http://www.amphastar.com/role/DisclosureInventoriesDetails Inventories (Details) Details http://www.amphastar.com/role/DisclosureInventoriesTables 65 false false R66.htm 99941101 - Disclosure - Property, Plant, and Equipment (Summary of Property, Plant, and Equipment) (Details) Sheet http://www.amphastar.com/role/DisclosurePropertyPlantAndEquipmentSummaryOfPropertyPlantAndEquipmentDetails Property, Plant, and Equipment (Summary of Property, Plant, and Equipment) (Details) Details http://www.amphastar.com/role/DisclosurePropertyPlantAndEquipmentTables 66 false false R67.htm 99941102 - Disclosure - Property, Plant, and Equipment (Narrative) (Details) Sheet http://www.amphastar.com/role/DisclosurePropertyPlantAndEquipmentNarrativeDetails Property, Plant, and Equipment (Narrative) (Details) Details http://www.amphastar.com/role/DisclosurePropertyPlantAndEquipmentTables 67 false false R68.htm 99941201 - Disclosure - Accounts Payable and Accrued Liabilities (Details) Sheet http://www.amphastar.com/role/DisclosureAccountsPayableAndAccruedLiabilitiesDetails Accounts Payable and Accrued Liabilities (Details) Details http://www.amphastar.com/role/DisclosureAccountsPayableAndAccruedLiabilitiesTables 68 false false R69.htm 99941301 - Disclosure - Debt (Schedule of Debt) (Details) Sheet http://www.amphastar.com/role/DisclosureDebtScheduleOfDebtDetails Debt (Schedule of Debt) (Details) Details http://www.amphastar.com/role/DisclosureDebtTables 69 false false R70.htm 99941302 - Disclosure - Debt (Narrative) (Details) Sheet http://www.amphastar.com/role/DisclosureDebtNarrativeDetails Debt (Narrative) (Details) Details http://www.amphastar.com/role/DisclosureDebtTables 70 false false R71.htm 99941303 - Disclosure - Debt (Long-Term Debt Maturities) (Details) Sheet http://www.amphastar.com/role/DisclosureDebtLongTermDebtMaturitiesDetails Debt (Long-Term Debt Maturities) (Details) Details http://www.amphastar.com/role/DisclosureDebtTables 71 false false R72.htm 99941401 - Disclosure - Income Taxes (Summary of Income (Loss) Before Income Taxes) (Details) Sheet http://www.amphastar.com/role/DisclosureIncomeTaxesSummaryOfIncomeLossBeforeIncomeTaxesDetails Income Taxes (Summary of Income (Loss) Before Income Taxes) (Details) Details http://www.amphastar.com/role/DisclosureIncomeTaxesTables 72 false false R73.htm 99941402 - Disclosure - Income Taxes (Narrative) (Details) Sheet http://www.amphastar.com/role/DisclosureIncomeTaxesNarrativeDetails Income Taxes (Narrative) (Details) Details http://www.amphastar.com/role/DisclosureIncomeTaxesTables 73 false false R74.htm 99941403 - Disclosure - Income Taxes (Summary of Provision for Income Taxes) (Details) Sheet http://www.amphastar.com/role/DisclosureIncomeTaxesSummaryOfProvisionForIncomeTaxesDetails Income Taxes (Summary of Provision for Income Taxes) (Details) Details http://www.amphastar.com/role/DisclosureIncomeTaxesTables 74 false false R75.htm 99941404 - Disclosure - Income Taxes (Reconciliation of the Statutory Federal Income Tax Rate to the Effective Tax Rate) (Details) Sheet http://www.amphastar.com/role/DisclosureIncomeTaxesReconciliationOfStatutoryFederalIncomeTaxRateToEffectiveTaxRateDetails Income Taxes (Reconciliation of the Statutory Federal Income Tax Rate to the Effective Tax Rate) (Details) Details http://www.amphastar.com/role/DisclosureIncomeTaxesTables 75 false false R76.htm 99941405 - Disclosure - Income Taxes (Income Taxes Paid) (Details) Sheet http://www.amphastar.com/role/DisclosureIncomeTaxesIncomeTaxesPaidDetails Income Taxes (Income Taxes Paid) (Details) Details http://www.amphastar.com/role/DisclosureIncomeTaxesTables 76 false false R77.htm 99941406 - Disclosure - Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) Sheet http://www.amphastar.com/role/DisclosureIncomeTaxesScheduleOfDeferredTaxAssetsAndLiabilitiesDetails Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) Details http://www.amphastar.com/role/DisclosureIncomeTaxesTables 77 false false R78.htm 99941407 - Disclosure - Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) Sheet http://www.amphastar.com/role/DisclosureIncomeTaxesReconciliationOfUnrecognizedTaxBenefitsDetails Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) Details http://www.amphastar.com/role/DisclosureIncomeTaxesTables 78 false false R79.htm 99941408 - Disclosure - Income Taxes (Uncertain Income Tax Positions - Narrative) (Details) Sheet http://www.amphastar.com/role/DisclosureIncomeTaxesUncertainIncomeTaxPositionsNarrativeDetails Income Taxes (Uncertain Income Tax Positions - Narrative) (Details) Details http://www.amphastar.com/role/DisclosureIncomeTaxesTables 79 false false R80.htm 99941501 - Disclosure - Stockholders' Equity (Share Buyback Program) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquityShareBuybackProgramDetails Stockholders' Equity (Share Buyback Program) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 80 false false R81.htm 99941502 - Disclosure - Stockholders' Equity (The 2015 Equity Incentive Plan) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquity2015EquityIncentivePlanDetails Stockholders' Equity (The 2015 Equity Incentive Plan) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 81 false false R82.htm 99941503 - Disclosure - Stockholders' Equity (2014 Employee Stock Purchase Plan) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquity2014EmployeeStockPurchasePlanDetails Stockholders' Equity (2014 Employee Stock Purchase Plan) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 82 false false R83.htm 99941504 - Disclosure - Stockholders' Equity (Key Assumptions Used in Determining Fair Value of Options Granted) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquityKeyAssumptionsUsedInDeterminingFairValueOfOptionsGrantedDetails Stockholders' Equity (Key Assumptions Used in Determining Fair Value of Options Granted) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 83 false false R84.htm 99941505 - Disclosure - Stockholders' Equity (Summary of Option Activity) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquitySummaryOfOptionActivityDetails Stockholders' Equity (Summary of Option Activity) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 84 false false R85.htm 99941506 - Disclosure - Stockholders' Equity (Information Relating to Option Grants and Exercises) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquityInformationRelatingToOptionGrantsAndExercisesDetails Stockholders' Equity (Information Relating to Option Grants and Exercises) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 85 false false R86.htm 99941507 - Disclosure - Stockholders' Equity (Summary of Nonvested Options) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquitySummaryOfNonvestedOptionsDetails Stockholders' Equity (Summary of Nonvested Options) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 86 false false R87.htm 99941508 - Disclosure - Stockholders' Equity (Restricted Stock Units) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquityRestrictedStockUnitsDetails Stockholders' Equity (Restricted Stock Units) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 87 false false R88.htm 99941509 - Disclosure - Stockholders' Equity (Information Relating to RSU Grants and Deliveries) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquityInformationRelatingToRsuGrantsAndDeliveriesDetails Stockholders' Equity (Information Relating to RSU Grants and Deliveries) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 88 false false R89.htm 99941510 - Disclosure - Stockholders' Equity (Share-Based Compensation Expense Included in the Statement of Operations) (Details) Sheet http://www.amphastar.com/role/DisclosureStockholdersEquityShareBasedCompensationExpenseIncludedInStatementOfOperationsDetails Stockholders' Equity (Share-Based Compensation Expense Included in the Statement of Operations) (Details) Details http://www.amphastar.com/role/DisclosureStockholdersEquityTables 89 false false R90.htm 99941601 - Disclosure - Employee Benefits (Details) Sheet http://www.amphastar.com/role/DisclosureEmployeeBenefitsDetails Employee Benefits (Details) Details http://www.amphastar.com/role/DisclosureEmployeeBenefits 90 false false R91.htm 99941701 - Disclosure - Commitments and Contingencies (Lease Expense) (Details) Sheet http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesLeaseExpenseDetails Commitments and Contingencies (Lease Expense) (Details) Details http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesTables 91 false false R92.htm 99941702 - Disclosure - Commitments and Contingencies (Lease Cash Flow Information) (Details) Sheet http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesLeaseCashFlowInformationDetails Commitments and Contingencies (Lease Cash Flow Information) (Details) Details http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesTables 92 false false R93.htm 99941702 - Disclosure - Commitments and Contingencies (Licensing Agreement) (Details) Sheet http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesLicensingAgreementDetails Commitments and Contingencies (Licensing Agreement) (Details) Details http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesTables 93 false false R94.htm 99941703 - Disclosure - Commitments and Contingencies (Future Minimum Rental Payments) (Details) Sheet http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesFutureMinimumRentalPaymentsDetails Commitments and Contingencies (Future Minimum Rental Payments) (Details) Details http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesTables 94 false false R95.htm 99941704 - Disclosure - Commitments and Contingencies (BAQSIMI) (Details) Sheet http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesBaqsimiDetails Commitments and Contingencies (BAQSIMI) (Details) Details http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesTables 95 false false R96.htm 99941705 - Disclosure - Commitments and Contingencies (Purchase Commitments) (Details) Sheet http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesPurchaseCommitmentsDetails Commitments and Contingencies (Purchase Commitments) (Details) Details http://www.amphastar.com/role/DisclosureCommitmentsAndContingenciesTables 96 false false R97.htm 99941801 - Disclosure - Related-Party Transactions (Details) Sheet http://www.amphastar.com/role/DisclosureRelatedPartyTransactionsDetails Related-Party Transactions (Details) Details http://www.amphastar.com/role/DisclosureRelatedPartyTransactions 97 false false R98.htm 99941901 - Disclosure - Litigation (Details) Sheet http://www.amphastar.com/role/DisclosureLitigationDetails Litigation (Details) Details http://www.amphastar.com/role/DisclosureLitigation 98 false false R99.htm 99942001 - Disclosure - Subsequent Events (Details) Sheet http://www.amphastar.com/role/DisclosureSubsequentEventsDetails Subsequent Events (Details) Details http://www.amphastar.com/role/DisclosureSubsequentEvents 99 false false All Reports Book All Reports amph-20251231.xsd amph-20251231_cal.xml amph-20251231_def.xml amph-20251231_lab.xml amph-20251231_pre.xml amph-20251231x10k.htm amph-20251231x10k001.jpg http://fasb.org/srt/2025 http://fasb.org/us-gaap/2025 http://xbrl.sec.gov/cyd/2025 http://xbrl.sec.gov/dei/2025 http://xbrl.sec.gov/ecd/2025 true true