Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	$ (146.0)	$ (172.8)	$ (153.7)	$ (164.9)
Balance, January 1, 2018	(145.7)	(159.3)	(145.7)	(159.3)
Other comprehensive income (loss), before reclassifications, net of tax	(7.8)	0.9	2.8	10.0
Amounts reclassified from accumulated other comprehensive income, net of tax	8.1	12.6	5.2	(4.4)
Other comprehensive income (loss), net of tax	0.3	13.5	8.0	5.6
Accumulated other comprehensive income (loss), net of tax ending balance	(145.7)	(159.3)	(145.7)	(159.3)
Other comprehensive income (loss), net of tax	0.3	13.5	8.0	5.6
Gains (losses) on securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	9.8	(14.5)	(25.0)	(15.7)
Balance, January 1, 2018	(31.2)	0.0	(31.2)	0.0
Other comprehensive income (loss), before reclassifications, net of tax	(49.1)	2.5	(11.4)	2.3
Amounts reclassified from accumulated other comprehensive income, net of tax	8.1	12.0	5.2	13.4
Other comprehensive income (loss), net of tax	(41.0)	14.5	(6.2)	15.7
Accumulated other comprehensive income (loss), net of tax ending balance	(31.2)	0.0	(31.2)	0.0
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)	(13.4)	(2.6)	15.1
Balance, January 1, 2018	(2.4)	16.2	(2.4)	16.2
Other comprehensive income (loss), before reclassifications, net of tax	0.3	29.0	0.2	18.9
Amounts reclassified from accumulated other comprehensive income, net of tax	0.0	0.6	0.0	(17.8)
Other comprehensive income (loss), net of tax	0.3	29.6	0.2	1.1
Accumulated other comprehensive income (loss), net of tax ending balance	(2.4)	16.2	(2.4)	16.2
Unfunded status of postretirement benefit plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance		(0.4)		(1.1)
Balance, January 1, 2018		(0.5)		(0.5)
Other comprehensive income (loss), before reclassifications, net of tax		(0.1)		0.6
Amounts reclassified from accumulated other comprehensive income, net of tax		0.0		0.0
Other comprehensive income (loss), net of tax		(0.1)		0.6
Accumulated other comprehensive income (loss), net of tax ending balance		(0.5)		(0.5)
Currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax beginning balance	(153.1)	(144.5)	(126.1)	(163.2)
Balance, January 1, 2018	(112.1)	(175.0)	(112.1)	(175.0)
Other comprehensive income (loss), before reclassifications, net of tax	41.0	(30.5)	14.0	(11.8)
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	41.0	(30.5)	14.0	(11.8)
Accumulated other comprehensive income (loss), net of tax ending balance	$ (112.1)	$ (175.0)	$ (112.1)	$ (175.0)