CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income (loss)	$ (34.1)	$ 17.4	$ (998.6)
Other comprehensive income (loss), before tax:
Foreign currency translation gain (loss)	(3.7)	1.2	0.7
Cash flow hedges:
Gains (losses) arising in period	(51.6)	3.5	6.3
Reclassification of losses (gains) to net income (loss)	1.1	(25.2)	36.3
Unrealized holding gains on securities:
Unrealized holding gains (losses) arising in period	0	0.2	0.9
Pension and OPEB plans:
Prior service credit (cost) arising in period	10.9	(6.1)	83.9
Gains (losses) arising in period	(422.5)	422.3	(240.4)
Reclassification of prior service cost (credits) included in net income (loss)	(68.9)	(76.2)	(71.1)
Reclassification of losses (gains) included in net income (loss)	6.9	25.3	181.8
Other comprehensive income (loss), before tax	(527.8)	345.0	(1.6)
Income tax expense related to items of other comprehensive income (loss)	0	22.7	0
Other comprehensive income (loss)	(527.8)	322.3	(1.6)
Comprehensive income (loss)	(561.9)	339.7	(1,000.2)
Less: Comprehensive income attributable to noncontrolling interests	62.8	64.2	28.7
Comprehensive income (loss) attributable to AK Steel Holding Corporation	$ (624.7)	$ 275.5	$ (1,028.9)