General - Narrative (Details) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)
Noncontrolling Interest [Line Items]
Employee service share-based compensation, tax benefit realized from exercise of stock options	$ 2	$ 5
CNAF Consolidated \| Loews
Noncontrolling Interest [Line Items]
Ownership percentage of outstanding common stock of CNAF	89.00%	89.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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