Financial Risk Management Activities - Credit Risk - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Outstanding letters of credit	$ 113	$ 397
Discontinued Operations
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Outstanding letters of credit		$ 240
Government [Member] | Continuing Operations
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	18.00%
Other [Member] | Continuing Operations
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	14.00%
Integrated Oil Companies | Continuing Operations
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	58.00%
Financial Institutions | Continuing Operations
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	10.00%