Financial Instruments - Additional Information (Detail) $ in Millions	6 Months Ended
Jun. 30, 2015 USD ($)
Offsetting [Abstract]
Estimated amount reclassified from other comprehensive income to interest expense	$ 115
Estimated termination value if there is breach of provision related to derivative agreement	$ 170

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