Fair Value Measurements and Financial Instruments - Notional Amounts of Outstanding Derivative Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 20,173	$ 13,099
Cross currency swaps
Derivative [Line Items]
Notional Amount	16,638	12,890
Interest rate caps
Derivative [Line Items]
Notional Amount	$ 2,840	$ 2,540

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