LONG-TERM INCENTIVE COMPENSATION - Schedule of Equity-Classified Stock-Based Compensation Costs (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share-Based Payment Arrangement, Noncash Expense [Abstract]
Equity-classified awards – expensed	$ 5	$ 4	$ 12	$ 5
Equity-classified awards – capitalized	$ 2	$ 0	$ 5	$ 1

Represents the compensation cost capitalized during the period arising from equity-based and liability-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

No definition available.

Name:	swn_ShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount
Namespace Prefix:	swn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration