Exit and Disposal Costs - Financial Statement Classification of Costs and Expenses Associated with Corporation's Restructuring Program (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Employee Severance [Member]
Restructuring Cost And Reserve [Line Items]
Employee Severance	$ 76	$ 252
Employee Severance [Member] | Exploration Expenses, Including Dry Holes and Lease Impairment [Member]
Restructuring Cost And Reserve [Line Items]
Employee Severance	3	19
Employee Severance [Member] | Operating Costs and Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Employee Severance	5	22
Employee Severance [Member] | General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Employee Severance	27	63
Employee Severance [Member] | Income from discontinued operations [Member]
Restructuring Cost And Reserve [Line Items]
Employee Severance	41	148
Facility and Other Exit Costs [Member]
Restructuring Cost And Reserve [Line Items]
Facility and Other Exit Costs	65	220
Facility and Other Exit Costs [Member] | Operating Costs and Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Facility and Other Exit Costs		1
Facility and Other Exit Costs [Member] | General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Facility and Other Exit Costs	(2)	54
Facility and Other Exit Costs [Member] | Income from discontinued operations [Member]
Restructuring Cost And Reserve [Line Items]
Facility and Other Exit Costs	70	141
Facility and Other Exit Costs [Member] | Other Net [Member]
Restructuring Cost And Reserve [Line Items]
Facility and Other Exit Costs		8
Facility and Other Exit Costs [Member] | Depreciation​ Depletion​ And​ Amortization​ Expenses​[Member]
Restructuring Cost And Reserve [Line Items]
Facility and Other Exit Costs	$ (3)	$ 16