CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income	$ 63.0	$ 244.1	$ 164.9
Other comprehensive income, before tax:
Foreign currency translation gain (loss)	(0.6)	(1.7)	4.7
Cash flow hedges:
Gains (losses) arising in period	(31.5)	(5.6)	(11.5)
Reclassification of losses (gains) to net income	8.9	(10.3)	(6.1)
Pension and OPEB plans:
Prior service credit (cost) arising in period	0.0	11.1	4.7
Gains (losses) arising in period	50.5	(63.6)	94.2
Reclassification of prior service cost (credits) included in net income	(9.6)	(9.8)	(53.8)
Reclassification of losses (gains) included in net income	15.7	29.3	6.3
Other comprehensive income (loss), before tax	33.4	(50.6)	38.5
Income tax expense in other comprehensive income	1.4	0.0	0.0
Other comprehensive income (loss)	32.0	(50.6)	38.5
Comprehensive income	95.0	193.5	203.4
Less: Comprehensive income attributable to noncontrolling interests	51.8	58.1	61.4
Comprehensive income attributable to AK Steel Holding Corporation	$ 43.2	$ 135.4	$ 142.0