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Commitments for Potential Future Investments

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of investment in equity security without readily determinable fair value.

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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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Amount of gain (loss) included in earnings for investments classified as other.

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Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 01, 2021	Nov. 30, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity method investments	$ 215	$ 207
Gain (loss) on equity securities	11	5	$ (27)
Other investments	42	$ 36
Proceeds from sale of other investments	62
Gain (loss) on sale of other investments	$ (4)
Marsh India
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Percentage of interest acquired	92.00%	49.00%		92.00%	49.00%
Private Insurance and Consulting
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity method investments	$ 56	$ 58
Private Equity Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity method investments	159	149
Equity method income	18	56	$ 3
Commitments for potential future investments	160
Equity Investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, fair value	$ 17	$ 75
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revenue target period	2 years	2 years
Minimum \| Marsh India
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Percentage of interest acquired		49.00%
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revenue target period	4 years	4 years
Maximum \| Marsh India
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Percentage of interest acquired		92.00%