Financial Risk Management - Gross Notional Volumes of Corporation's Derivative Contracts Outstanding (Detail)	Jun. 30, 2015 USD ($) MMBbls	Dec. 31, 2014 USD ($)
Interest rate swap [Member]
Derivative [Line Items]
Derivative notional amount	$ 1,300,000,000	$ 1,300,000,000
Gross Volumes of the Financial Risk Management Derivative Contracts Outstanding [Member] | Foreign Exchange [Member]
Derivative [Line Items]
Derivative notional amount	947,000,000	1,189,000,000
Gross Volumes of the Financial Risk Management Derivative Contracts Outstanding [Member] | Interest rate swap [Member]
Derivative [Line Items]
Derivative notional amount	$ 1,300,000,000	$ 1,300,000,000
Gross Volumes of the Financial Risk Management Derivative Contracts Outstanding [Member] | Commodity, Primarily Crude Oil (Millions of Barrels) [Member]
Derivative [Line Items]
Absolute volume of derivative commodity contracts | MMBbls	13