Derivative Financial Instruments - Notional Values of Derivative Contracts (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Total	$ 419	$ 1,765
Currency swaps [Member]
Derivatives, Fair Value [Line Items]
Total	216	1,562
Derivatives designated as hedging instruments [Member] \| Currency swaps [Member]
Derivatives, Fair Value [Line Items]
Total	$ 203	$ 203

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant