Debt and Financing Arrangements (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 15, 2018
Williams Partners L.P. [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 3,500.0
Commercial paper, outstanding	0.0
$3.5 billion credit facility [Member]
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount	0.0
Additional Amount By Which Credit Facility Can Be Increased	500.0
Line of credit facility, amount outstanding	0.0
$3.5 billion credit facility [Member] | Williams Partners L.P. [Member] | Commercial paper [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	3,000.0
$3.5 billion credit facility [Member] | Williams Partners L.P. [Member] | Letter of credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,125.0
4%SeniorUnsecuredNotesDue2028
Line of Credit Facility [Line Items]
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%