Label	Element	Value
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	alk_TaxCutsandJobsActReclassificationfromAOCItoRetainedEarningsTaxEffect	$ 3,000,000
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	9,000,000
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation	0
Stock Issued During Period, Value, Employee Stock Purchase Plan	us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	0
Dividends, Cash	us-gaap_DividendsCash	45,000,000
AOCI Attributable to Parent [Member]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	alk_TaxCutsandJobsActReclassificationfromAOCItoRetainedEarningsTaxEffect	0
Retained Earnings [Member]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	alk_TaxCutsandJobsActReclassificationfromAOCItoRetainedEarningsTaxEffect	$ 3,000,000

Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect

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Amount of increase to additional paid-in capital (APIC) for recognition of cost for award under share-based payment arrangement.

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Amount of paid and unpaid cash dividends declared for classes of stock, for example, but not limited to, common and preferred.

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Aggregate change in value for stock issued during the period as a result of employee stock purchase plan.

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Value, after forfeiture, of shares issued under share-based payment arrangement. Excludes employee stock ownership plan (ESOP).

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