Other Comprehensive Income (Loss) (Schedule of Items Reclassified out of AOCL) (Details) - USD ($)	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified	$ (60,500,000)	$ (60,500,000)	$ (120,200,000)	$ (120,200,000)	$ (238,400,000)	$ (219,600,000)	$ (238,400,000)	$ (219,600,000)
Tax effect		11,300,000		26,300,000	43,300,000	39,000,000.0
Net of tax		49,200,000		93,900,000	195,100,000	180,600,000
Net activity		13,700,000		11,400,000	40,700,000	(29,700,000)		(29,700,000)
Stockholders' Equity Attributable to Parent		1,821,000,000.0	1,726,100,000		1,821,000,000.0			1,726,100,000
Available-for-sale Securities and Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		5,200,000		(2,900,000)	(13,700,000)	(2,400,000)
Net of tax		(3,900,000)		(2,100,000)	(10,500,000)	(1,800,000)
Prior to reclassification		6,900,000		(6,000,000.0)	29,000,000.0	(39,700,000)
Other Comprehensive Income (Loss), before Tax		1,700,000		(8,900,000)	15,300,000	(42,100,000)
Other Comprehensive Income (Loss), Tax		500,000		2,200,000	(3,600,000)	9,700,000
Net activity		1,200,000		(6,700,000)	11,700,000	(32,400,000)
Stockholders' Equity Attributable to Parent		(17,600,000)	(29,300,000)	(25,200,000)	(17,600,000)	(25,200,000)		(29,300,000)	$ (18,800,000)	$ (18,500,000)	$ 7,200,000
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		0		0	0	0
Prior to reclassification		11,700,000		17,100,000	26,500,000	8,600,000
Other Comprehensive Income (Loss), before Tax		11,700,000		17,100,000	26,500,000	8,600,000
Other Comprehensive Income (Loss), Tax		0		0	0	0
Net activity		11,700,000		17,100,000	26,500,000	8,600,000
Stockholders' Equity Attributable to Parent		(84,200,000)	(110,700,000)	(136,800,000)	(84,200,000)	(136,800,000)		(110,700,000)	(95,900,000)	(153,900,000)	(145,400,000)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		1,200,000		1,400,000	3,700,000	(7,700,000)
Tax effect		(300,000)		(600,000)	(900,000)	1,700,000
Prior to reclassification		(100,000)		200,000	(300,000)	100,000
Other Comprehensive Income (Loss), before Tax		1,100,000		1,600,000	3,400,000	(7,600,000)
Other Comprehensive Income (Loss), Tax		(300,000)		(600,000)	(900,000)	1,700,000
Net activity		800,000		1,000,000.0	2,500,000	(5,900,000)
Stockholders' Equity Attributable to Parent		(37,700,000)	(40,200,000)	(50,200,000)	(37,700,000)	(50,200,000)		(40,200,000)	(38,500,000)	(51,200,000)	(44,300,000)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		(5,200,000)		(2,900,000)	(13,700,000)	(2,400,000)
Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		(4,000,000.0)		(1,500,000)	10,000,000.0	(10,100,000)
Prior to reclassification		18,500,000		11,300,000	55,200,000	(31,000,000.0)
Other Comprehensive Income (Loss), before Tax		14,500,000		9,800,000	45,200,000	(41,100,000)
Other Comprehensive Income (Loss), Tax		(800,000)		1,600,000	(4,500,000)	11,400,000
Net activity		13,700,000		11,400,000	40,700,000	(29,700,000)
Stockholders' Equity Attributable to Parent		(139,500,000)	(180,200,000)	(212,200,000)	(139,500,000)	(212,200,000)		(180,200,000)	(153,200,000)	(223,600,000)	(182,500,000)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax		900,000		(800,000)	2,800,000	(6,000,000.0)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax effect		1,300,000		800,000	3,200,000	600,000
Foreign Exchange Forward [Member] | Available-for-sale Securities and Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Tax		1,000,000.0		(800,000)	(200,000)	(1,000,000.0)
Net activity		700,000		(600,000)	(200,000)	(800,000)
Stockholders' Equity Attributable to Parent		(500,000)	(300,000)	(600,000)	(500,000)	(600,000)		(300,000)	(1,200,000)	0	200,000
Foreign Exchange Forward [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Tax		(300,000)		200,000	0	200,000
Interest Rate Swap [Member] | Available-for-sale Securities and Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Tax		3,400,000		(4,600,000)	20,500,000	(43,000,000.0)
Net activity		2,600,000		(3,500,000)	15,800,000	(33,100,000)
Stockholders' Equity Attributable to Parent		(19,900,000)	(35,700,000)	(38,300,000)	(19,900,000)	(38,300,000)		(35,700,000)	(22,500,000)	(34,800,000)	(5,200,000)
Interest Rate Swap [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		(4,000,000.0)		(1,700,000)	(10,700,000)	(1,300,000)
Tax effect		1,000,000.0		400,000	2,500,000	300,000
Net of tax		(3,000,000.0)		(1,300,000)	(8,200,000)	(1,000,000.0)
Prior to reclassification		7,400,000		(2,900,000)	31,200,000	(41,700,000)
Other Comprehensive Income (Loss), Tax		(800,000)		1,100,000	(4,700,000)	9,900,000
Foreign Exchange | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		(1,200,000)		(1,200,000)	(3,000,000.0)	(1,100,000)
Tax effect		300,000		400,000	700,000	300,000
Net of tax		(900,000)		(800,000)	(2,300,000)	(800,000)
Prior to reclassification		2,200,000		400,000	2,800,000	100,000
Currency Swap [Member] | Available-for-sale Securities and Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Stockholders' Equity Attributable to Parent			$ 6,700,000					$ 6,700,000	$ 4,900,000	$ 16,300,000	$ 12,200,000
Currency Swap [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		0		0	0	0
Prior to reclassification		(2,700,000)		(3,500,000)	(5,000,000.0)	1,900,000
Other Comprehensive Income (Loss), Tax		600,000		900,000	1,100,000	(400,000)
Foreign Exchange Contract [Member] | Available-for-sale Securities and Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Tax		(2,700,000)		(3,500,000)	(5,000,000.0)	1,900,000
Net activity		(2,100,000)		(2,600,000)	(3,900,000)	1,500,000
Stockholders' Equity Attributable to Parent		$ 2,800,000		$ 13,700,000	$ 2,800,000	$ 13,700,000