Consolidated Balance Sheets (Parenthetical) $ in Millions	Sep. 30, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares
Statement of Financial Position [Abstract]
Available for sale, at amortized cost	$ 82,254	$ 79,536
Fixed maturities available for sale, hybrid financial instruments	0	2
Held to maturity, at Fair Value	10,365	10,670
Equity securities, at cost	723	706
Other investments, cost	$ 4,429	$ 4,270
Common Shares, shares issued | shares	479,783,864	479,783,864
Common Shares, shares outstanding | shares	464,158,519	465,968,716
Common Shares in treasury, shares | shares	15,625,345	13,815,148