Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Long-Term Debt - CEI Senior Notes due 2027 (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jul. 06, 2020	Dec. 31, 2019
Long-term debt
Interest rate (as a percent)	4.30%
CEI Senior Notes
Long-term debt
Interest rate (as a percent)	8.13%	8.125%
CEI Senior Notes \| Estimate of Fair Value Measurement
Long-term debt
Long-term debt, gross		$ 1,800
CEI Senior Notes \| Reported Value Measurement
Long-term debt
Long-term debt, gross	$ 1,767		$ 0