Consolidated Balance Sheets (Parenthetical) $ in Millions	Mar. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares
Statement of Financial Position [Abstract]
Available for sale, at amortized cost	$ 79,624	$ 79,323
Fixed maturities available for sale, hybrid financial instruments	8	9
Held to maturity, at Fair Value	13,240	13,259
Equity securities, at cost	0
Other investments, cost	$ 0
Common Shares, shares issued \| shares	479,783,864	479,783,864
Common Shares, shares outstanding \| shares	458,179,205	459,203,378
Common Shares in treasury, shares \| shares	21,604,659	20,580,486

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value as of the balance sheet date of hybrid instruments.

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Includes other investments and securities that are not at fair value as of the balance sheet date and those that are not accounted for under the equity method.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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