Pension and Savings Plans - Textual (Details)	3 Months Ended	12 Months Ended
	Apr. 01, 2017 numberOfPlan	Dec. 31, 2021	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of 401(k) plans | numberOfPlan	3
Paid discretionary contributions to defined contribution pension plans, company match			$ 9,600,000	$ 27,800,000	$ 30,300,000
Discretionary contributions to defined contribution pension plans, granted			0	0
Payment of prior performance contributions			0	8,900,000	8,500,000
Australia
Defined Benefit Plan Disclosure [Line Items]
Paid discretionary contributions to defined contribution pension plans, company match			20,500,000	26,500,000	31,600,000
Discretionary contributions to defined contribution pension plans, granted			0	0
Payment of prior performance contributions			0	3,000,000	3,000,000
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Payment for settlement			51,600,000	0
Settlement gain			$ 2,700,000	$ 0	$ 0
Expected long-term return on plan assets			3.60%	4.20%	5.65%
Accumulated benefit obligation			$ 816,400,000	$ 853,800,000
Defined benefit plan, assets			$ 847,500,000	855,200,000	$ 764,800,000
Percentage of company's qualified pension plans on a GAAP accounting basis			80.00%
Peabody Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, assets			$ 672,500,000	689,400,000
Plan with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation			632,900,000	675,900,000
Western Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, assets			175,000,000.0	165,800,000
Plan with accumulated benefit obligation in excess of plan assets, accumulated benefit obligation			$ 183,500,000	$ 177,900,000
Fixed Income Investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percentage			100.00%
Real Estate
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation, percentage			1.00%	1.00%
Scenario, Forecast | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Expected long-term return on plan assets		2.80%