Significant Transactions - NSM (Details) - USD ($) $ in Millions		12 Months Ended
	Aug. 01, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Other Significant Noncash Transactions [Line Items]
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group		$ 0.0	$ 2.9	$ 0.0
NSM
Other Significant Noncash Transactions [Line Items]
Net gain (loss) from sale of discontinued operations, net of tax		$ 0.0	886.8	0.0
Discontinued Operations, Disposed of by Sale | NSM
Other Significant Noncash Transactions [Line Items]
Disposal group, consideration	$ 1,400.0
Net transaction gain	875.7
Net gain (loss) from sale of discontinued operations, net of tax	886.8		886.8	0.0
Net gain (loss) from foreign currency translation from sale of discontinued operations, net of tax - NSM Group	2.9		2.9	0.0
General and administrative expenses	$ 14.0		$ 126.8	$ 190.4