CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income	$ 244.1	$ 164.9	$ 49.2
Other comprehensive income, before tax:
Foreign currency translation gain (loss)	(1.7)	4.7	(1.5)
Cash flow hedges:
Gains (losses) arising in period	(5.6)	(11.5)	56.1
Reclassification of losses (gains) to net income	(10.3)	(6.1)	39.1
Pension and OPEB plans:
Prior service credit (cost) arising in period	11.1	4.7	(8.3)
Gains (losses) arising in period	(63.6)	94.2	11.6
Reclassification of prior service cost (credits) included in net income	(9.8)	(53.8)	(54.8)
Reclassification of losses (gains) included in net income	29.3	6.3	97.9
Other comprehensive income (loss), before tax	(50.6)	38.5	140.1
Income tax expense in other comprehensive income	0.0	0.0	15.5
Other comprehensive income (loss)	(50.6)	38.5	124.6
Comprehensive income	193.5	203.4	173.8
Less: Comprehensive income attributable to noncontrolling interests	58.1	61.4	66.0
Comprehensive income attributable to AK Steel Holding Corporation	$ 135.4	$ 142.0	$ 107.8