Impairment (Tables)

12 Months Ended

Dec. 31, 2018

Impairments and Exploration Expenses [Abstract]

Fair Value Measurements, Nonrecurring [Table Text Block]

The following table summarizes impairment charges of proved properties from continuing operations. Additionally, it presents the values of assets, by major category, measured at fair value on a nonrecurring basis in periods subsequent to their initial recognition.

	2018				2017				2016
(In millions)	Fair Value		Impairment		Fair Value		Impairment		Fair Value		Impairment
Long-lived assets held for use	$	113	$	75	$	179	$	229	$	15	$	67

Exploration Expenses [Table Text Block]

The following table summarizes impairment charges of unproved properties included as a component of exploration expense:

	Year Ended December 31,
(In millions)	2018		2017		2016
Exploration Expenses
Unproved property impairments	$	208	$	246	$	195
Dry well costs	47		77		25
Geological and geophysical	21		25		5
Other	13		61		98
Total exploration expenses	$	289	$	409	$	323