Consolidated Balance Sheets (Parenthetical) $ in Millions	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares
Statement of Financial Position [Abstract]
Fixed maturities available for sale, at amortized cost	$ 77,835	$ 79,536
Fixed maturities available for sale, hybrid financial instruments	5	2
Held-to-maturity Securities, Fair Value	14,474	10,670
Equity securities, at cost	737	706
Other investments, cost	$ 4,417	$ 4,270
Common Shares, shares issued | shares	479,783,864	479,783,864
Common Shares, shares outstanding | shares	463,833,179	465,968,716
Common Shares in treasury, shares | shares	15,950,685	13,815,148