Asset Impairment Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 0	$ 116	$ 6	$ 116
Kilroot and Ballylumford [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use	0	115	0	115
Assets Carrying Amount Disclosure Nonrecurring		114		114
Other Subsidiaries [Member]
Asset Impairment Expense [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 0	$ 1	$ 6	$ 1