Consolidated Balance Sheets (Parenthetical) $ in Millions	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares
Statement of Financial Position [Abstract]
Fixed maturities available for sale, at amortized cost	$ 79,323	$ 77,835
Fixed maturities available for sale, hybrid financial instruments	9	5
Debt Securities, Held-to-maturity, Fair Value	13,259	14,474
Equity Securities, FV-NI, Cost	770
Equity securities, at cost		737
Other investments, cost	$ 5,277	$ 4,417
Common Shares, shares issued \| shares	479,783,864	479,783,864
Common Shares, shares outstanding \| shares	459,203,378	463,833,179
Common Shares in treasury, shares \| shares	20,580,486	15,950,685

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

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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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