Reserve for Future Policy Benefits and Separate Account Liabilities Level 4 Separate Accounts by Major Category of Investment (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Schedule of Fair Value of Separate Accounts by Major Category of Investment, Fair Value	$ 37,208	$ 36,925
Invested in Fixed Income Securities	15.00%	16.00%
Invested in Equity Securities	85.00%	84.00%
Equity Securities [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Schedule of Fair Value of Separate Accounts by Major Category of Investment, Fair Value	$ 34,496	$ 33,880
Cash and Cash Equivalents [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Schedule of Fair Value of Separate Accounts by Major Category of Investment, Fair Value	$ 2,712	$ 3,045