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

Allocated Share-based Compensation Expense, Equity-based and Liability-based, Amount of Unvested Portion of Share-based Awards Forfeited that are Excluded

No definition available.

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

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

Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount, Amount of Unvested Portion of Share-based Awards Forfeited that are Excluded

No definition available.

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

Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]

No definition available.