Subsequent Events (Details) (Subsequent Event [Member], Merger [Member])	3 Months Ended
	Mar. 31, 2015
Subsequent Event [Member] | Merger [Member]
Subsequent Event [Line Items]
For each publicly held WPZ common unit held the ratio of conversion to ACMP common units	0.86672
For publicly held ACMP units, ratio for additional units to be issued	0.06152
Net effective exchange ratio for Williams held WPZ common units	0.82080
Master limited partnership, ownership percentage	60.00%