Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2015

Accounting Policies [Abstract]

Non-Cash Write-Downs of Carrying Value of Proved Oil and Gas Properties by Country

The following tables present non-cash write-downs of the carrying value of the Company’s proved oil and gas properties by country for the third quarter and first nine months of 2015 and 2014:

	For the Quarter Ended September 30, 2015				For the Quarter Ended September 30, 2014
	Before tax		After tax		Before tax		After tax
	(In millions)
U.S.	$	4,301	$	2,774	$	1,545	$	995
Canada		973		719		—		—
North Sea		447		223		17		7
Total impairment	$	5,721	$	3,716	$	1,562	$	1,002

	For the Nine Months Ended September 30, 2015				For the Nine Months Ended September 30, 2014
	Before tax		After tax		Before tax		After tax
	(In millions)
U.S.	$	13,855	$	8,937	$	1,545	$	995
Canada		3,160		2,347		—		—
North Sea		1,742		871		220		84
Total impairment	$	18,757	$	12,155	$	1,765	$	1,079