Acquisitions - Gross Carrying Amount and Weighted-Average Useful Life Allocated to Intangible Assets (Details) - Elan Financial Services $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($)
Business Acquisition [Line Items]
Gross Carrying Amount	$ 353
Weighted-Average Useful Life	15 years
Customer related intangible assets
Business Acquisition [Line Items]
Gross Carrying Amount	$ 350
Weighted-Average Useful Life	15 years
Trade name
Business Acquisition [Line Items]
Gross Carrying Amount	$ 3
Weighted-Average Useful Life	8 years

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
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- Definition

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.

+ References

No definition available.

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- Definition

The amount of identifiable intangible assets recognized as of the acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 55
-Paragraph 37
-URI http://asc.fasb.org/extlink&oid=116868840&loc=d3e2207-128464

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