Debt and Banking Arrangements Long-term Debt Issuances and Retirements (Details 1) - USD ($) $ in Millions			3 Months Ended
	Jun. 15, 2018	Mar. 28, 2018	Mar. 31, 2018	Mar. 15, 2018	Mar. 05, 2018
Williams Partners L.P. [Member] | 4.875% Senior Unsecured Notes due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt interest rate		4.875%
Long-term debt retired		$ 750
Williams Partners L.P. [Member] | 4.85%SeniorUnsecuredNotesDue2048 [Member]
Debt Instrument [Line Items]
Long-term debt face amount					$ 800
Long-term debt interest rate					4.85%
Transcontinental Gas Pipe Line Company, LLC [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Other Long-term Debt			$ 19
Transcontinental Gas Pipe Line Company, LLC [Member] | 4%SeniorUnsecuredNotesDue2028 [Member]
Debt Instrument [Line Items]
Long-term debt face amount				$ 400
Long-term debt interest rate				4.00%
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] | 4.6%SeniorUnsecuredNotesDue2048 [Member]
Debt Instrument [Line Items]
Long-term debt face amount				$ 600
Long-term debt interest rate				4.60%
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%
Subsequent Event [Member] | Transcontinental Gas Pipe Line Company, LLC [Member] | 6.05% Senior Unsecured Notes due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt interest rate	6.05%
Long-term debt retired	$ 250