Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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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.

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Segment Information (Narrative) (Details) $ in Millions	3 Months Ended								12 Months Ended
Segment Information (Narrative) (Details) $ in Millions	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) Segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting [Abstract]
Number of segments \| Segment									5
Segment Reporting Information [Line Items]
Revenues	$ 17,143	$ 18,678	$ 17,497	$ 16,302	$ 15,662	$ 16,289	$ 21,185	$ 14,805	$ 69,620	$ 67,941	$ 62,308
Total assets	740,463				687,538				$ 740,463	$ 687,538
Concentration Risk, Percentage									10.00%	10.00%	10.00%
Japan
Segment Reporting Information [Line Items]
Total assets	134,000				120,000				$ 134,000	$ 120,000
Assets, Total \| Geographic Concentration Risk \| Japan
Segment Reporting Information [Line Items]
Concentration Risk, Percentage									18.00%	17.00%
U.S.
Segment Reporting Information [Line Items]
Total assets	$ 266,174				$ 248,174				$ 266,174	$ 248,174
U.S. \| One U.S. Customer
Segment Reporting Information [Line Items]
Revenues										$ 6,000
U.S. \| One U.S. Customer \| Sales
Segment Reporting Information [Line Items]
Concentration Risk, Percentage										12.00%