Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2013

Earnings Per Share [Abstract]

Earnings per share

	Three Months Ended March 31,
	2013			2012
Net income (loss) attributable to AK Steel Holding Corporation	$	(9.9	)	$	(11.8	)
Less: distributed earnings to common stockholders and holders of certain stock compensation awards	—			5.5
Undistributed earnings (loss)	$	(9.9	)	$	(17.3	)
Common stockholders earnings—basic and diluted:
Distributed earnings to common stockholders	$	—		$	5.5
Undistributed earnings (loss) to common stockholders	(9.8		)	(17.2		)
Common stockholders earnings (loss)—basic and diluted	$	(9.8	)	$	(11.7	)
Common shares outstanding (weighted-average shares in millions):
Common shares outstanding for basic earnings per share	135.7			110.0
Effect of exchangeable debt	—			—
Effect of dilutive stock-based compensation	—			—
Common shares outstanding for diluted earnings per share	135.7			110.0
Basic and diluted earnings per share:
Distributed earnings	$	—		$	0.05
Undistributed earnings (loss)	(0.07		)	(0.16		)
Basic and diluted earnings (loss) per share	$	(0.07	)	$	(0.11	)
Potentially issuable common shares (in millions) excluded from earnings per share calculation due to anti-dilutive effect	2.4			1.9