Exploration Expense (Tables)

3 Months Ended

Mar. 31, 2018

Impairments and Exploration Expense [Abstract]

Details of Impairment of Long-Lived Assets Held and Used by Asset [Table Text Block]

Exploration Expenses [Table Text Block]

The following table summarizes the components of exploration expenses:

	Three Months Ended March 31,
(In millions)	2018		2017
Exploration Expenses
Unproved property impairments	$	40	$	20
Dry well costs	2		—
Geological and geophysical	6		1
Other	4		7
Total exploration expenses	$	52	$	28