Business Acquisition, Percentage of Interests Acquired, Planned Acquisition

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Equity Method Investment, Shares Owned

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Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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- Definition

This item represents the aggregate value of each identified investment accounted for under the equity method of accounting based on the quoted market price for those investments in common stock for which a quoted market price is available.

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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 after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Amount before tax and reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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Amount of investments classified as other.

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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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Price of a single share of a number of saleable stocks of a company.

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Fair Value Measurements (Equity Method Investments, Summarized Financial Information) (Details) shares in Millions, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 R / shares	Dec. 31, 2016 R / shares
Schedule of Equity Method Investments [Line Items]
Impairment charge	$ 83
Carrying value of equity method investments		$ 287	$ 405
Other investments		75	56
Unrealized investment (loss) income		0	(7)	$ 21
Alexander Forbes Group Holdings Limited
Schedule of Equity Method Investments [Line Items]
Carrying value of equity method investments		$ 144
Equity investment shares owned by the Company (in shares) \| shares		443
Share price \| R / shares					R 5.14
Market value of equity method investment		$ 159
Alexander Forbes Group Holdings Limited \| Mercer Consulting Group
Schedule of Equity Method Investments [Line Items]
Percentage of interest acquired						33.00%
Share price \| R / shares						R 7.50
Benefitfocus
Schedule of Equity Method Investments [Line Items]
Unrealized investment (loss) income		54
Private Equity Funds
Schedule of Equity Method Investments [Line Items]
Carrying value of equity method investments		82	76
Investment (loss) income		16	14
Corporate stocks
Schedule of Equity Method Investments [Line Items]
Investments, fair value		146	100
Other Investments
Schedule of Equity Method Investments [Line Items]
Unrealized investment (loss) income		$ 1	$ 1