Share Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions			9 Months Ended	12 Months Ended
	Nov. 21, 2020	Nov. 21, 2019	Jul. 13, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, right to purchase						700,000
Annual Management Incentive Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share based compensation expense				$ 16.9	$ 9.5	$ 13.8
HRG Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, available for issuance				1,400,000
HRG Equity Plan [Member] | HRG [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining unrecognized pre-tax compensation cost				$ 0.0
HRG Equity Plan [Member] | Common Stock [Member] | HRG [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized issuance shares				24,000,000
HRG Warrant Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, outstanding				0
HRG Warrant Plan [Member] | Common Stock [Member] | Former Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, right to purchase				3,000,000
Exercise price per share				$ 13.125
Shares, vested				600,000
Vesting period				4 years
Estimated grant date fair value				$ 9.6
Spectrum Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, available for issuance				600,000
Restricted Stock Units [Member] | Specturm And SB/RH [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining unrecognized pre-tax compensation cost				$ 41.6
Restricted Stock Units [Member] | HRG [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, right to purchase						100,000
Restricted Stock Units [Member] | Long-Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				3 years
Restricted Stock Units [Member] | Long-Term Incentive Plan [Member] | Performance [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time-based service conditions pecentage				70.00%
Restricted Stock Units [Member] | Long-Term Incentive Plan [Member] | Service [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time-based service conditions pecentage				30.00%
Restricted Stock Units [Member] | Bridge Awards [Member] | Performance [Member] | Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time-based service conditions pecentage	60.00%	60.00%
Restricted Stock Units [Member] | Bridge Awards [Member] | Service [Member] | Forecast [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Time-based service conditions pecentage	40.00%	40.00%
Stock Options [Member] | HRG [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, right to purchase			2,500,000			500,000
Exercise price per share						$ 15.39
Total fair value vested				$ 0.2	0.8
Intrinsic value of options exercised					21.5
Cash settlement					$ 19.9
Shares, vested and exercisable				200,000
Weighted average exercise price of vested and exercisable				$ 73.51
Maximum [Member] | Spectrum Equity Plan [Member] | Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized issuance shares				7,100,000