Revenue Recognition (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Abstract]
Revenue from contracts		$ 761	$ 644
Other (1)	[1]	(6)	(6)
Revenues		$ 755	$ 638

[1] Primarily consists of income from ARPs and leases. ARPs are contracts between Houston Electric and the PUCT, not between Houston Electric and a customer. Houston Electric recognizes ARP revenue as other revenues when the PUCT-specified conditions for recognition have been met. Upon recovery of ARP revenue through incorporation in rates charged for utility service to customers, ARP revenue is reversed and recorded as revenue from contracts with customers. The recognition of ARP revenues and the reversal of ARP revenues upon recovery through rates charged for utility service may not occur in the same period.