CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income (loss)	$ 6.8	$ (6.9)
Other comprehensive income (loss), before tax:
Foreign currency translation gain (loss)	(1.1)	0.8
Cash flow hedges:
Gains (losses) arising in period	(3.0)	(17.0)
Reclassification of losses (gains) to net income (loss)	(3.9)	7.8
Unrealized holding gains (losses) on securities:
Unrealized holding gains (losses) arising in period	0.1	0.7
Pension and OPEB plans:
Reclassification of prior service cost (credits) included in net income (loss)	(19.1)	(18.2)
Reclassification of losses (gains) included in net income (loss)	7.3	6.1
Other comprehensive income (loss), before tax	(19.7)	(19.8)
Income tax provision (benefit) related to items of comprehensive income (loss)	0	(7.7)
Other comprehensive income (loss)	(19.7)	(12.1)
Comprehensive income (loss)	(12.9)	(19.0)
Less: Comprehensive income attributable to noncontrolling interests	16.7	4.9
Comprehensive income (loss) attributable to AK Steel Holding Corporation	$ (29.6)	$ (23.9)