CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Millions, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2009	$ 880.1	$ 1.2	$ 1,911.4	$ (162.2)	$ (1,037.5)	$ 167.9	$ (0.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(130.7)
Net income (loss) attributable to AK Steel Holding Corporation	(128.9)				(128.9)
Noncontrolling interests-net income (loss)	(2.9)						(2.9)
Share-based compensation	15.8		15.8
Stock options exercised	1.3		1.3
Tax provision from share-based compensation	(19.1)		(19.1)
Purchase of treasury stock	(7.9)			(7.9)
Change in accumulated other comprehensive income	(75.3)					(75.3)
Common stock dividends	(22.0)				(22.0)
Balance at Dec. 31, 2010	641.1	1.2	1,909.4	(170.1)	(1,188.4)	92.6	(3.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(160.1)				(155.6)		(4.5)
Net income (loss) attributable to AK Steel Holding Corporation	(155.6)
Share-based compensation	14.9		14.9
Stock options exercised	0.2		0.2
Tax provision from share-based compensation	(2.3)		(2.3)
Purchase of treasury stock	(1.5)			(1.5)
Change in accumulated other comprehensive income	(89.9)					(89.9)
Common stock dividends	(22.0)				(22.0)
Distributions to noncontrolling interests	(3.2)						(3.2)
Balance at Dec. 31, 2011	377.2	1.2	1,922.2	(171.6)	(1,366.0)	2.7	(11.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(998.6)				(1,027.3)		28.7
Net income (loss) attributable to AK Steel Holding Corporation	(1,027.3)
Issuance of common stock	96.4	0.3	96.1
Issuance of exchange option in Exchangeable Notes	37.3		37.3
Share-based compensation	14.6		14.6
Tax provision from share-based compensation	(0.5)		(0.5)
Purchase of treasury stock	(1.7)			(1.7)
Change in accumulated other comprehensive income	(1.6)					(1.6)
Common stock dividends	(11.0)				(11.0)
Increase in noncontrolling interest as a result of SunCoke financing activities	416.1						416.1
Distributions to noncontrolling interests	(36.8)						(36.8)
Income tax payable assumed by noncontrolling interests	17.6						17.6
Balance at Dec. 31, 2012	$ (91.0)	$ 1.5	$ 2,069.7	$ (173.3)	$ (2,404.3)	$ 1.1	$ 414.3