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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

DEBT - Energen Notes (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Nov. 29, 2018
Energen Notes
Debt Instrument [Line Items]
Long-term debt, gross			$ 530
4.625% Notes due 2021
Debt Instrument [Line Items]
Long-term debt, gross	$ 399	$ 400
Stated interest rate	4.625%
7.125% Medium-term Notes, Series B, due 2028
Debt Instrument [Line Items]
Long-term debt, gross	$ 108	100
Stated interest rate	7.125%
7.320% Medium-term Notes, Series A, due 2022
Debt Instrument [Line Items]
Long-term debt, gross	$ 21	20
Stated interest rate	7.32%
7.350% Medium-term Notes, Series A, due 2027
Debt Instrument [Line Items]
Long-term debt, gross	$ 11	$ 10
Stated interest rate	7.35%