Other Comprehensive Income (Loss) - Schedule of changes in accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Balance at the beginning of the period	$ (102.8)
Other comprehensive income before reclassifications
Before tax amount	61.0	$ 18.6
Tax expense	(0.4)	(0.3)
After tax amount	60.6	18.3
Amounts reclassified from accumulated other comprehensive loss(1)	1.6	1.5
Total changes in other comprehensive income, net of tax	62.2	19.8
Balance at the end of the period	(40.7)
Pension and Postretirement
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Balance at the beginning of the period	(69.6)	(62.3)
Other comprehensive income before reclassifications
Before tax amount	0.0	0.0
Tax expense	0.0	0.0
After tax amount	0.0	0.0
Amounts reclassified from accumulated other comprehensive loss(1)	1.2	1.1
Total changes in other comprehensive income, net of tax	1.2	1.1
Reclassification of certain income tax effects			$ (6.0)
Balance at the end of the period	(68.4)	(67.2)
Currency Translation
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Balance at the beginning of the period	(21.1)	(64.7)
Other comprehensive income before reclassifications
Before tax amount	59.2	17.4
Tax expense	0.0	0.0
After tax amount	59.2	17.4
Amounts reclassified from accumulated other comprehensive loss(1)	0.0	0.0
Total changes in other comprehensive income, net of tax	59.2	17.4
Reclassification of certain income tax effects			0.0
Balance at the end of the period	38.1	(47.3)
Net Unrealized Gain (Loss) on Derivative Instruments
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Balance at the beginning of the period	(12.1)	(13.6)
Other comprehensive income before reclassifications
Before tax amount	1.7	1.3
Tax expense	(0.4)	(0.3)
After tax amount	1.3	1.0
Amounts reclassified from accumulated other comprehensive loss(1)	0.4	0.4
Total changes in other comprehensive income, net of tax	1.7	1.4
Reclassification of certain income tax effects			0.0
Balance at the end of the period	(10.4)	(12.2)
Total Attributable to Hillenbrand, Inc.
Accumulated Other Comprehensive Income (Loss), before Tax [Roll Forward]
Balance at the beginning of the period	(102.8)	(140.6)
Other comprehensive income before reclassifications
Before tax amount	60.9	18.7
Tax expense	(0.4)	(0.3)
After tax amount	60.5	18.4
Amounts reclassified from accumulated other comprehensive loss(1)	1.6	1.5
Total changes in other comprehensive income, net of tax	62.1	19.9
Reclassification of certain income tax effects			$ (6.0)
Balance at the end of the period	(40.7)	(126.7)
Noncontrolling Interests
Other comprehensive income before reclassifications
Before tax amount	0.1	(0.1)
Tax expense	0.0	0.0
After tax amount	0.1	(0.1)
Amounts reclassified from accumulated other comprehensive loss(1)	0.0	0.0
Total changes in other comprehensive income, net of tax	$ 0.1	$ (0.1)