Unrestricted Subsidiaries - Income Statement Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Unrestricted Subsidiaries
Sales	$ 1,026.6	$ 1,133.7	$ 2,020.5	$ 2,139.5
Cost of sales	1,070.2	1,069.9	2,145.5	1,997.2
Gross profit (loss)	(43.6)	63.8	(125.0)	142.3
Operating costs and expenses:
General and administrative	41.1	37.5	53.2	60.8
Other operating expense	4.1	5.0	9.2	10.2
Operating income (loss)	(101.0)	6.2	(149.7)	42.5
Other income (expense):
Interest expense	(52.9)	(56.8)	(111.4)	(117.6)
Gain (loss) on derivative instruments	4.3	11.3	(2.9)	(5.6)
Debt extinguishment costs	(0.1)	(0.1)	(47.7)	(0.3)
Other income	2.0	0.8	2.4	1.0
Total other expense	(46.7)	(44.8)	(159.6)	(122.5)
Net loss before income taxes	(147.7)	(38.6)	(309.3)	(80.0)
Income tax benefit (expenses)	0.2	0.5	0.6	0.7
Net loss	(147.9)	(39.1)	(309.9)	(80.7)
Unrestricted Subsidiaries
Unrestricted Subsidiaries
Sales	208.9	182.9	374.5	333.2
Cost of sales	234.3	179.4	426.4	363.4
Gross profit (loss)	(25.4)	3.5	(51.9)	(30.2)
Operating costs and expenses:
General and administrative	8.8	6.9	18.5	13.4
Other operating expense	0.4	1.3	1.9	2.8
Operating income (loss)	(34.6)	(4.7)	(72.3)	(46.4)
Other income (expense):
Interest expense	(18.1)	(21.9)	(42.9)	(46.5)
Gain (loss) on derivative instruments		3.5	(5.6)	5.9
Debt extinguishment costs			(47.6)
Other income	1.9	0.2	2.7	0.5
Total other expense	(16.2)	(18.2)	(93.4)	(40.1)
Net loss	$ (50.8)	$ (22.9)	$ (165.7)	$ (86.5)