Other Comprehensive Income (Loss) (Schedule of Items Reclassified out of AOCL) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified	$ (120,200,000)	$ (45,700,000)	$ (219,600,000)	$ (156,000,000.0)
Tax effect	26,300,000	13,100,000	39,000,000.0	31,700,000
Net of tax	(93,900,000)	(32,600,000)	(180,600,000)	(124,300,000)
Net activity	11,400,000	(4,900,000)	(29,700,000)	(26,800,000)
Stockholders' Equity Attributable to Parent	1,652,400,000		1,652,400,000			$ 1,573,300,000
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	(2,900,000)	(1,400,000)	(2,400,000)	(5,400,000)
Net of tax	(2,100,000)	(1,200,000)	(1,800,000)	(4,100,000)
Prior to reclassification	(6,000,000.0)	(10,800,000)	(39,700,000)	(14,200,000)
Other Comprehensive Income (Loss), before Tax	(8,900,000)	(12,200,000)	(42,100,000)	(19,600,000)
Other Comprehensive Income (Loss), Tax	(2,200,000)	(2,800,000)	(9,700,000)	(4,600,000)
Net activity	(6,700,000)	(9,400,000)	(32,400,000)	(15,000,000.0)
Stockholders' Equity Attributable to Parent	(25,200,000)	2,600,000	(25,200,000)	2,600,000	$ (18,500,000)	7,200,000	$ 12,000,000.0	$ 16,800,000
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	17,100,000	4,100,000	8,600,000	(13,100,000)
Other Comprehensive Income (Loss), before Tax	17,100,000	4,100,000	8,600,000	(13,100,000)
Other Comprehensive Income (Loss), Tax	0	0	0	0
Net activity	17,100,000	4,100,000	8,600,000	(13,100,000)
Stockholders' Equity Attributable to Parent	(136,800,000)	(118,400,000)	(136,800,000)	(118,400,000)	(153,900,000)	(145,400,000)	(122,500,000)	(105,300,000)
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	1,400,000	700,000	(7,700,000)	1,800,000
Tax effect	(600,000)	(300,000)	1,700,000	(6,800,000)
Prior to reclassification	200,000	0	100,000	100,000
Other Comprehensive Income (Loss), before Tax	1,600,000	700,000	(7,600,000)	1,900,000
Other Comprehensive Income (Loss), Tax	(600,000)	(300,000)	1,700,000	(600,000)
Net activity	1,000,000.0	400,000	(5,900,000)	1,300,000
Stockholders' Equity Attributable to Parent	(50,200,000)	(29,400,000)	(50,200,000)	(29,400,000)	(51,200,000)	(44,300,000)	(29,800,000)	(24,500,000)
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	2,900,000	1,400,000	2,400,000	5,400,000
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	(1,500,000)	(700,000)	(10,100,000)	(3,600,000)
Prior to reclassification	11,300,000	(6,700,000)	(31,000,000.0)	(27,200,000)
Other Comprehensive Income (Loss), before Tax	9,800,000	(7,400,000)	(41,100,000)	(30,800,000)
Other Comprehensive Income (Loss), Tax	(1,600,000)	(2,500,000)	11,400,000	4,000,000.0
Net activity	11,400,000	(4,900,000)	(29,700,000)	(26,800,000)
Stockholders' Equity Attributable to Parent	(212,200,000)	(145,200,000)	(212,200,000)	(145,200,000)	(223,600,000)	(182,500,000)	(140,300,000)	(113,000,000.0)
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	800,000	400,000	(6,000,000.0)	(5,000,000.0)
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	800,000	200,000	600,000	1,300,000
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	(800,000)	(400,000)	(1,000,000.0)	(100,000)
Net activity	(600,000)	(300,000)	(800,000)	(100,000)
Stockholders' Equity Attributable to Parent	(600,000)	100,000	(600,000)	100,000	0	200,000	400,000	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	200,000	100,000	200,000	0
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	(4,600,000)	(10,800,000)	(43,000,000.0)	(28,800,000)
Net activity	(3,500,000)	(8,300,000)	(33,100,000)	(22,100,000)
Stockholders' Equity Attributable to Parent	(38,300,000)	(3,000,000.0)	(38,300,000)	(3,000,000.0)	(34,800,000)	(5,200,000)	5,300,000	18,300,000
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	1,700,000	1,800,000	1,300,000	5,600,000
Tax effect	400,000	200,000	300,000	1,300,000
Net of tax	1,300,000	1,600,000	1,000,000.0	4,300,000
Prior to reclassification	(2,900,000)	(9,000,000.0)	(41,700,000)	(23,200,000)
Other Comprehensive Income (Loss), Tax	1,100,000	2,500,000	9,900,000	6,700,000
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	(400,000)	1,100,000	(200,000)
Tax effect	400,000	0	300,000	0
Net of tax	800,000	(400,000)	800,000	(200,000)
Prior to reclassification	400,000	(800,000)	100,000	(300,000)
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					$ 16,300,000	$ 12,200,000	$ 6,300,000	$ (1,700,000)
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	(3,500,000)	(1,000,000.0)	1,900,000	9,300,000
Other Comprehensive Income (Loss), Tax	900,000	200,000	(400,000)	(2,100,000)
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	(3,500,000)	(1,000,000.0)	1,900,000	9,300,000
Net activity	(2,600,000)	(800,000)	1,500,000	7,200,000
Stockholders' Equity Attributable to Parent	$ 13,700,000	$ 5,500,000	$ 13,700,000	$ 5,500,000