Subsidiary Guarantors (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
ASSETS
Accounts receivable - related parties	$ 0	$ 0
Other current assets	535	546
Oil and natural gas properties, net	12,587	11,086
Property and equipment, net	232	216
Investment in subsidiaries	0	0
Other long-term assets	128	271
Total assets	13,482	12,119
LIABILITIES AND EQUITY
Accounts payable - related parties	0	0
Other current liabilities	810	753
Long-term debt	2,738	2,741
Other long-term liabilities	1,303	1,002
Equity	8,631	7,623
Total liabilities and stockholders' equity	13,482	12,119
Consolidation Eliminations [Member]
ASSETS
Accounts receivable - related parties	(8,250)	(8,655)
Other current assets	0	0
Oil and natural gas properties, net	0	0
Property and equipment, net	0	0
Investment in subsidiaries	(2,963)	(1,989)
Other long-term assets	0	0
Total assets	(11,213)	(10,644)
LIABILITIES AND EQUITY
Accounts payable - related parties	(8,250)	(8,655)
Other current liabilities	0	0
Long-term debt	0	0
Other long-term liabilities	0	0
Equity	(2,963)	(1,989)
Total liabilities and stockholders' equity	(11,213)	(10,644)
Parent Company [Member] | Reportable Legal Entities [Member]
ASSETS
Accounts receivable - related parties	8,903	8,991
Other current assets	14	12
Oil and natural gas properties, net	0	0
Property and equipment, net	0	0
Investment in subsidiaries	2,963	1,989
Other long-term assets	42	11
Total assets	11,922	11,003
LIABILITIES AND EQUITY
Accounts payable - related parties	(653)	(336)
Other current liabilities	50	114
Long-term debt	2,738	2,741
Other long-term liabilities	1,156	861
Equity	8,631	7,623
Total liabilities and stockholders' equity	11,922	11,003
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
ASSETS
Accounts receivable - related parties	(653)	(336)
Other current assets	515	534
Oil and natural gas properties, net	11,968	11,086
Property and equipment, net	232	216
Investment in subsidiaries	0	0
Other long-term assets	86	260
Total assets	12,148	11,760
LIABILITIES AND EQUITY
Accounts payable - related parties	8,290	8,991
Other current liabilities	756	639
Long-term debt	0	0
Other long-term liabilities	141	141
Equity	2,961	1,989
Total liabilities and stockholders' equity	12,148	$ 11,760
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
ASSETS
Accounts receivable - related parties	0
Other current assets	6
Oil and natural gas properties, net	619
Property and equipment, net	0
Investment in subsidiaries	0
Other long-term assets	0
Total assets	625
LIABILITIES AND EQUITY
Accounts payable - related parties	613
Other current liabilities	4
Long-term debt	0
Other long-term liabilities	6
Equity	2
Total liabilities and stockholders' equity	$ 625