Income Taxes - Tax Carryforwards Table (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Foreign Tax Credits [Member]
Tax Carryforwards [Line Items]
Tax credit carryforward	$ 1,254
Foreign Tax Credits [Member] | Earliest Tax Year [Member]
Tax Carryforwards [Line Items]
Tax credit carryforward, expiration date	Dec. 31, 2023
Foreign Tax Credits [Member] | Latest Tax Year [Member]
Tax Carryforwards [Line Items]
Tax credit carryforward, expiration date	Dec. 31, 2026
Texas Margins Tax Credit [Member]
Tax Carryforwards [Line Items]
Tax credit carryforward	$ 33
Tax credit carryforward, expiration date	Dec. 31, 2026
Foreign [Member]
Tax Carryforwards [Line Items]
Net operating loss carryforward	$ 1,264
Foreign [Member] | Earliest Tax Year [Member]
Tax Carryforwards [Line Items]
Net operating loss carryforwards, expiration date	Dec. 31, 2016
State [Member]
Tax Carryforwards [Line Items]
Net operating loss carryforward	$ 4,762
State [Member] | Earliest Tax Year [Member]
Tax Carryforwards [Line Items]
Net operating loss carryforwards, expiration date	Dec. 31, 2016
State [Member] | Latest Tax Year [Member]
Tax Carryforwards [Line Items]
Net operating loss carryforwards, expiration date	Dec. 31, 2035