Financial Instruments - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Estimated amount reclassified from other comprehensive income and reduce interest expense	$ 5

The estimated value of gains (losses), net anticipated to be transferred in the future from accumulated other comprehensive income into earnings.

No definition available.

Name:	us-gaap_DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration