Other Comprehensive Income (Loss) (Schedule of Items Reclassified out of AOCL) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified	$ (56,800,000)	$ (60,700,000)	$ (99,400,000)	$ (110,300,000)
Tax effect	9,900,000	11,200,000	12,700,000	18,600,000
Net of tax	(46,900,000)	(49,500,000)	(86,700,000)	(91,700,000)
Net activity	(62,300,000)	(5,000,000.0)	(41,100,000)	(21,900,000)
Stockholders' Equity Attributable to Parent	1,548,900,000		1,548,900,000			$ 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	(400,000)	(1,800,000)	500,000	(4,000,000.0)
Net of tax	(300,000)	(1,400,000)	300,000	(2,900,000)
Prior to reclassification	(29,500,000)	(1,700,000)	(33,700,000)	(3,400,000)
Other Comprehensive Income (Loss), before Tax	(29,900,000)	(3,500,000)	(33,200,000)	(7,400,000)
Other Comprehensive Income (Loss), Tax	(6,800,000)	(1,600,000)	(7,500,000)	(1,800,000)
Net activity	(23,100,000)	(1,900,000)	(25,700,000)	(5,600,000)
Stockholders' Equity Attributable to Parent	(18,500,000)	12,000,000.0	(18,500,000)	12,000,000.0	$ 4,600,000	7,200,000	$ 13,900,000	$ 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	(31,600,000)	(3,600,000)	(8,500,000)	(17,200,000)
Other Comprehensive Income (Loss), before Tax	(31,600,000)	(3,600,000)	(8,500,000)	(17,200,000)
Other Comprehensive Income (Loss), Tax	0	0	0	0
Net activity	(31,600,000)	(3,600,000)	(8,500,000)	(17,200,000)
Stockholders' Equity Attributable to Parent	(153,900,000)	(122,500,000)	(153,900,000)	(122,500,000)	(122,300,000)	(145,400,000)	(118,900,000)	(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	(10,300,000)	600,000	(9,100,000)	1,100,000
Tax effect	2,600,000	(200,000)	2,300,000	(6,500,000)
Prior to reclassification	100,000	100,000	(100,000)	100,000
Other Comprehensive Income (Loss), before Tax	(10,200,000)	700,000	(9,200,000)	1,200,000
Other Comprehensive Income (Loss), Tax	2,600,000	(200,000)	2,300,000	(300,000)
Net activity	(7,600,000)	500,000	(6,900,000)	900,000
Stockholders' Equity Attributable to Parent	(51,200,000)	(29,800,000)	(51,200,000)	(29,800,000)	(43,600,000)	(44,300,000)	(30,300,000)	(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	400,000	1,800,000	(500,000)	4,000,000.0
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	(10,700,000)	(1,200,000)	(8,600,000)	(2,900,000)
Prior to reclassification	(61,000,000.0)	(5,200,000)	(42,300,000)	(20,500,000)
Other Comprehensive Income (Loss), before Tax	(71,700,000)	(6,400,000)	(50,900,000)	(23,400,000)
Other Comprehensive Income (Loss), Tax	(9,400,000)	(1,400,000)	9,800,000	1,500,000
Net activity	(62,300,000)	(5,000,000.0)	(41,100,000)	(21,900,000)
Stockholders' Equity Attributable to Parent	(223,600,000)	(140,300,000)	(223,600,000)	(140,300,000)	(161,300,000)	(182,500,000)	(135,300,000)	(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	(7,700,000)	400,000	(6,800,000)	(5,400,000)
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	100,000	400,000	(200,000)	1,100,000
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	0	(800,000)	(200,000)	300,000
Net activity	0	(500,000)	(200,000)	200,000
Stockholders' Equity Attributable to Parent	0	400,000	0	400,000	0	200,000	900,000	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	0	300,000	0	(100,000)
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	(40,100,000)	(10,800,000)	(38,400,000)	(18,000,000.0)
Net activity	(30,900,000)	(8,500,000)	(29,600,000)	(13,800,000)
Stockholders' Equity Attributable to Parent	(34,800,000)	5,300,000	(34,800,000)	5,300,000	(3,900,000)	(5,200,000)	13,800,000	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	400,000	1,700,000	(400,000)	3,800,000
Tax effect	100,000	500,000	(100,000)	1,100,000
Net of tax	300,000	1,200,000	(300,000)	2,700,000
Prior to reclassification	(39,700,000)	(9,100,000)	(38,800,000)	(14,200,000)
Other Comprehensive Income (Loss), Tax	9,200,000	2,300,000	8,800,000	4,200,000
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	0	100,000	(100,000)	200,000
Tax effect	0	(100,000)	(100,000)	0
Net of tax	0	200,000	0	200,000
Prior to reclassification	0	(700,000)	(300,000)	500,000
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					$ 8,500,000	$ 12,200,000	$ (800,000)	$ (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	10,200,000	8,100,000	5,400,000	10,300,000
Other Comprehensive Income (Loss), Tax	(2,400,000)	(1,000,000.0)	(1,300,000)	(2,300,000)
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	10,200,000	8,100,000	5,400,000	10,300,000
Net activity	7,800,000	7,100,000	4,100,000	8,000,000.0
Stockholders' Equity Attributable to Parent	$ 16,300,000	$ 6,300,000	$ 16,300,000	$ 6,300,000