Prepaid Expenses (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Prepaid Expenses [Abstract]
Prepaid drilling costs	$ 11,944	$ 7,275
Prepaid insurance	$ 59,406	$ 50,050

Carrying amount as of the balance sheet date of unamortized costs of insurance coverage, which will be ratably expensed or capitalized over the insurance coverage period; such periods expire within one year or the normal operating cycle, if longer.

No definition available.

Name:	swn_PrepaidInsuranceExpense
Namespace Prefix:	swn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant