Significant Accounting Policies (Narrative) (Detail) $ in Millions	12 Months Ended
Dec. 31, 2018 USD ($)
Reclassification Adjustment Increase Decrease In Insurance Loss Recoverable	$ 31

Represents Reclassification Adjustment Increase Decrease In Insurance Loss Recoverable.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration