Debt and Banking Arrangements Long-term Debt Issuances and Retirements (Details 1) - USD ($) $ in Millions	Jun. 15, 2016	Apr. 15, 2016	Jan. 22, 2016
Transcontinental Gas Pipe Line Company, LLC [Member] | 7.85% Senior Unsecured Notes Due 2026 [Member]
Debt Instrument [Line Items]
Long-term debt face amount			$ 1,000
Long-term debt interest rate			7.85%
Additional interest rate accrued for default of registration rights agreements first period			0.25%
Additional interest rate accrued for default of registration rights agreements each subsequent period			0.25%
Maximum additional interest rate accrued for default of registration rights agreements all periods			0.50%
Transcontinental Gas Pipe Line Company, LLC [Member] | 6.4% Senior Unsecured Notes due 2016 [Member]
Debt Instrument [Line Items]
Long-term debt interest rate		6.40%
Long-term debt retired		$ 200
Northwest Pipeline LLC [Member] | 7% Senior Unsecured Notes due 2016 [Member]
Debt Instrument [Line Items]
Long-term debt interest rate	7.00%
Long-term debt retired	$ 175