Fair Value of Financial Instruments and Fair Value Measurements - Level 3 Fair Value Measurements (Details) $ in Millions	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Black Scholes | Forecasted future revenue | Minimum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	830	1,100
Black Scholes | Forecasted future revenue | Maximum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	840	1,200
Black Scholes | Stated royalty rate | Minimum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.010	0.010
Black Scholes | Stated royalty rate | Maximum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.015	0.015
Black Scholes | Annualized volatility | Minimum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.139	0.094
Black Scholes | Annualized volatility | Maximum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.304	0.281
Black Scholes | Annualized volatility | Weighted Average | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.250	0.199
Fair Value, Measurements, Recurring | Discounted cash flow | Significant Unobservable Inputs (Level 3) | Discount rate | Notes Payable, UMWA Funds Settlement Liability, Enviromental Settlement Obligations, and Reclaimation Funding Liability,
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt and acquisition-related obligation, measurement input	0.35	0.21
Line of Credit | Fair Value, Measurements, Recurring | Discounted cash flow | ABL Facility - due April 2022 | Significant Unobservable Inputs (Level 3) | Discount rate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt, measurement input	0.10