Commitments and Contingencies (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
ACF
Loss Contingencies [Line Items]
Defined benefit plan underfunded amount	$ 110.0		$ 110.0
Starfire Holding Corporation
Loss Contingencies [Line Items]
Ownership percentage by Mr. Icahn	99.60%		99.60%
Pension funding indemnity agreement with subsidiary	$ 250.0		$ 250.0
Energy Segment
Loss Contingencies [Line Items]
RINs costs	16.0	$ 36.0	335.0	$ 71.0
RFS position	442.0		$ 442.0		$ 214.0
Icahn Enterprises G.P. | Mr. Icahn and affiliates
Loss Contingencies [Line Items]
Affiliate ownership in parent company general partner			100.00%
Accrued expenses and other liabilities
Loss Contingencies [Line Items]
Accrued environmental liabilities	$ 39.0		$ 39.0		$ 37.0
Icahn Enterprises Holdings | Mr. Icahn and affiliates
Loss Contingencies [Line Items]
Affiliate ownership interest			89.00%