Supplemental Cash Flow Information - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplementary Insurance Information
Non-cash modifications of certain mortgage loans, fixed income securities, limited partnership interests and other investments, as well as mergers completed with equity securities	$ 198	$ 94	$ 106
Non-cash financing activities related to the issuance of shares for vested restricted stock units	50	$ 32	43
Liabilities assumed			$ 90
Right-of-use asset obtained in exchange for operating lease liability	604
Operating lease, payments	155
Accounting Standards Update 2016-02
Supplementary Insurance Information
Right-of-use asset obtained in exchange for operating lease liability	$ 488