Accounts Receivable (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Accounts Notes And Loans Receivable [Line Items]
Accounts Receivable, Net, Current	$ 243	$ 232
Allowance for Doubtful Accounts Receivable, Current	(16)	(16)
Revenue
Accounts Notes And Loans Receivable [Line Items]
Accounts Receivable, Net, Current	149	163
Joint interest
Accounts Notes And Loans Receivable [Line Items]
Accounts Receivable, Net, Current	78	53
Other
Accounts Notes And Loans Receivable [Line Items]
Accounts Receivable, Net, Current	$ 32	$ 32