Summary Of Significant Accounting Policies - Narrative (Details) $ in Millions	Dec. 31, 2017 USD ($)
Accounting Standards Update 2014-09 \| Retained Earnings
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative impact of adjustment to retained earnings	$ 224

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant