Undistributed earnings (loss), attributable to parent

No definition available.

Name:	aks_UndistributedEarningsLossAttributableToParent
Namespace Prefix:	aks_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Antidilution
-URI http://asc.fasb.org/extlink&oid=6505113

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Diluted Earnings Per Share
-URI http://asc.fasb.org/extlink&oid=6510752

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Contingent Stock Agreement
-URI http://asc.fasb.org/extlink&oid=6508534

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income (loss) attributable to AK Steel Holding Corporation	$ (145.4)	$ 6.7	$ (64.0)	$ (306.3)	$ 13.5	$ (7.2)	$ (17.1)	$ (86.1)	$ (509.0)	$ (96.9)	$ (46.8)
Less: distributed earnings to common stockholders and holders of certain stock compensation awards									0.0	0.0	0.0
Undistributed earnings (loss)									(509.0)	(96.9)	(46.8)
Common stockholders earnings - basic [Abstract]
Distributed earnings to common stockholders									0.0	0.0	0.0
Undistributed earnings (loss) to common stockholders - basic									(507.3)	(96.6)	(46.6)
Common stockholders earnings (loss) - basic									(507.3)	(96.6)	(46.6)
Common stockholders earnings - diluted [Abstract]
Distributed earnings to common stockholders									0.0	0.0	0.0
Undistributed earnings to common stockholders - diluted									(507.3)	(96.6)	(46.6)
Common stockholders earnings - diluted									$ (507.3)	$ (96.6)	$ (46.6)
Common shares outstanding (weighted-average shares in millions) [Abstract]
Common shares outstanding for basic earnings per share (in shares)									177.2	148.1	135.8
Effect of exchangeable debt									0.0	0.0	0.0
Effect of dilutive stock-based compensation (in shares)									0.0	0.0	0.0
Common shares outstanding for diluted earnings per share (in shares)									177.2	148.1	135.8
Basic earnings per share [Abstract]
Distributed earnings - basic (in dollars per share)									$ 0.00	$ 0.00	$ 0.00
Undistributed earnings (loss) - basic (in dollars per share)									(2.86)	(0.65)	(0.34)
Basic earnings (loss) per share (in dollars per share)					$ 0.08	$ (0.05)	$ (0.13)	$ (0.63)	(2.86)	(0.65)	(0.34)
Diluted earnings per share [Abstract]
Distributed earnings - diluted (in dollars per share)									0.00	0.00	0.00
Undistributed earnings (loss) - diluted (in dollars per share)									(2.86)	(0.65)	(0.34)
Diluted earnings (loss) per share (in dollars per share)					$ 0.07	$ (0.05)	$ (0.13)	$ (0.63)	$ (2.86)	$ (0.65)	$ (0.34)
Potentially issuable common shares excluded from earnings per share calculation due to anti-dilutive effect (in millions of shares)									3.6	9.7	2.6