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Employee Benefit Plans - Performance-Based Restricted Stock Units (Details) - Performance Shares [Member] - USD ($) $ / shares in Units, $ in Millions	1 Months Ended				12 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense					$ 17.9	$ 8.7	$ 5.1
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of percentage of units vested upon achieving performance criteria					0.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of percentage of units vested upon achieving performance criteria					200.00%
November Two Thousand Sixteen Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target number of performance units				330,000
Granted, weighted average grant date fair value, per share				$ 29.20
Share-based compensation expense					$ 2.9	3.9	5.1
November Two Thousand Seventeen Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target number of performance units			330,000
Granted, weighted average grant date fair value, per share			$ 45.79
Share-based compensation expense					8.9	4.8	0.0
November Two Thousand Eighteen Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target number of performance units		360,000
Granted, weighted average grant date fair value, per share		$ 37.75
Share-based compensation expense					$ 6.1	$ 0.0	$ 0.0
Subsequent Event [Member] \| November Two Thousand Sixteen Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock awarded	495,000