Goodwill and Other Intangibles - Narrative (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in the goodwill balance during the period			$ 0
Goodwill	$ 207,000,000		207,000,000		$ 207,000,000
Amortizable intangible assets related to property and casualty insurance acquisitions	48,000,000		48,000,000		54,000,000
Accumulated amortization	45,000,000		45,000,000		$ 39,000,000
Amortization of intangible assets	$ 3,000,000	$ 2,000,000	$ 6,000,000	$ 4,000,000

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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-Name Accounting Standards Codification
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-SubTopic 10
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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase (decrease) of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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