Reinsurance (Effects of Reinsurance on Earnings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Premiums:
Direct premiums	$ 1,731	$ 2,226	$ 2,404
Reinsurance assumed	13	81	296
Reinsurance ceded	(916)	(1,127)	(1,063)
Net premiums	828	1,180	1,637
Universal life and investment-type product policy fees:
Direct universal life and investment-type product policy fees	3,653	3,582	3,722
Reinsurance assumed	103	126	139
Reinsurance ceded	(600)	(611)	(568)
Net universal life and investment-type product policy fees	3,156	3,097	3,293
Other revenues:
Direct other revenues	260	271	271
Reinsurance assumed	29	89	2
Reinsurance ceded	47	349	160
Net other revenues	336	709	433
Policyholder benefits and claims:
Direct policyholder benefits and claims	5,080	6,101	4,944
Reinsurance assumed	89	127	302
Reinsurance ceded	(1,575)	(2,490)	(2,159)
Net policyholder benefits and claims	3,594	3,738	3,087
Amortization of deferred policy acquisition costs and value of business acquired
Direct amortization of deferred policy acquisition costs and value of business acquired	$ 916	$ (225)	$ 673