Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	$ (160.5)	$ (172.0)	$ (153.7)	$ (164.9)
Balance, January 1, 2018	(146.0)	(172.8)	(146.0)	(172.8)
Other comprehensive income (loss), before reclassifications, net of tax	16.7	1.5	10.6	9.1
Amounts reclassified from accumulated other comprehensive income, net of tax	(2.2)	(2.3)	(2.9)	(17.0)
Other comprehensive income (loss), net of tax	14.5	(0.8)	7.7	(7.9)
Accumulated other comprehensive income (loss), net of tax ending balance	(146.0)	(172.8)	(146.0)	(172.8)
Other comprehensive income (loss), net of tax	14.5	(0.8)	7.7	(7.9)
Gains (losses) on securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	(10.3)	(10.0)	(25.0)	(15.7)
Balance, January 1, 2018	9.8	(14.5)	9.8	(14.5)
Other comprehensive income (loss), before reclassifications, net of tax	22.3	(5.5)	37.7	(0.2)
Amounts reclassified from accumulated other comprehensive income, net of tax	(2.2)	1.0	(2.9)	1.4
Other comprehensive income (loss), net of tax	20.1	(4.5)	34.8	1.2
Accumulated other comprehensive income (loss), net of tax ending balance	9.8	(14.5)	9.8	(14.5)
Gains (losses) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	(2.7)	(20.3)	(2.6)	15.1
Balance, January 1, 2018	(2.7)	(13.4)	(2.7)	(13.4)
Other comprehensive income (loss), before reclassifications, net of tax	0.0	10.2	(0.1)	(10.1)
Amounts reclassified from accumulated other comprehensive income, net of tax	0.0	(3.3)	0.0	(18.4)
Other comprehensive income (loss), net of tax	0.0	6.9	(0.1)	(28.5)
Accumulated other comprehensive income (loss), net of tax ending balance	(2.7)	(13.4)	(2.7)	(13.4)
Unfunded status of postretirement benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance		(0.6)		(1.1)
Balance, January 1, 2018		(0.4)		(0.4)
Other comprehensive income (loss), before reclassifications, net of tax		0.2		0.7
Amounts reclassified from accumulated other comprehensive income, net of tax		0.0		0.0
Other comprehensive income (loss), net of tax		0.2		0.7
Accumulated other comprehensive income (loss), net of tax ending balance		(0.4)		(0.4)
Currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	(147.5)	(141.1)	(126.1)	(163.2)
Balance, January 1, 2018	(153.1)	(144.5)	(153.1)	(144.5)
Other comprehensive income (loss), before reclassifications, net of tax	(5.6)	(3.4)	(27.0)	18.7
Amounts reclassified from accumulated other comprehensive income, net of tax	0.0	0.0	0.0	0.0
Other comprehensive income (loss), net of tax	(5.6)	(3.4)	(27.0)	18.7
Accumulated other comprehensive income (loss), net of tax ending balance	$ (153.1)	$ (144.5)	$ (153.1)	$ (144.5)