Acquisition of Severstal Dearborn (Details) (Subsequent Event [Member], Severstal Dearborn [Member], USD $) In Millions, unless otherwise specified	Jul. 19, 2014
Subsequent Event [Member] \| Severstal Dearborn [Member]
Business Acquisition [Line Items]
Business Acquisition Cost Of Acquired Entity Expected Purchase Price	$ 700.0

The amount expected to be paid to acquire an entity that has been announced but not yet completed

No definition available.

Name:	aks_BusinessAcquisitionCostOfAcquiredEntityExpectedPurchasePrice
Namespace Prefix:	aks_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant