Property, Plant and Equipment Classes and Depreciation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Public Utilities, Property, Plant and Equipment, Transmission and Distribution [Abstract]
Accumulated depreciation, depletion and amortization	$ (14,175)	$ (12,306)
Public Utilities, Property, Plant and Equipment, Equipment	35,704	35,113
Land and land rights-of-way	1,456	1,431
Construction work in process	2,995	2,161
Property, plant and equipment, net	40,155	38,705
Public Utilities, Property, Plant and Equipment, Common	14,055	12,900
Depreciation, depletion and amortization	2,261	2,209	$ 2,309
Charged against PPE [Member]
Public Utilities, Property, Plant and Equipment, Transmission and Distribution [Abstract]
Depreciation, depletion and amortization	2,022	1,970	$ 2,059
Gas Transmission Equipment [Member]
Public Utilities, Property, Plant and Equipment, Transmission and Distribution [Abstract]
Pipelines (Natural gas, liquids, crude oil and CO2)	20,157	19,341
Gas, Transmission and Distribution Equipment [Member]
Public Utilities, Property, Plant and Equipment, Transmission and Distribution [Abstract]
Equipment (Natural gas, liquids, crude oil, CO2, and terminals)	24,152	23,298
Property, Plant and Equipment, Other Types [Member]
Public Utilities, Property, Plant and Equipment, Transmission and Distribution [Abstract]
Other(a)	$ 5,570	$ 4,780