Supplemental Balance Sheet Information - Textuals (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net after-tax loss on derivatives reclassified from AOCI	$ 6

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