Reinsurance (Effects of Affiliated Reinsurance on Statements of Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Premiums:
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:
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:
Reinsurance assumed	29	89	2
Reinsurance ceded	47	349	160
Net other revenues	336	709	433
Policyholder benefits and claims:
Reinsurance assumed	89	127	302
Reinsurance ceded	(1,575)	(2,490)	(2,159)
Interest credited to policyholder account balances:
Direct amortization of deferred policy acquisition costs and value of business acquired	916	(225)	673
Affiliated Entity [Member] | Assumed
Premiums:
Reinsurance assumed	13	35	227
Universal life and investment-type product policy fees:
Reinsurance assumed	103	126	139
Other revenues:
Reinsurance assumed	29	59	2
Policyholder benefits and claims:
Reinsurance assumed	87	90	252
Affiliated Entity [Member] | Ceded
Premiums:
Reinsurance ceded	(537)	(766)	(687)
Universal life and investment-type product policy fees:
Reinsurance ceded	(14)	(60)	(58)
Other revenues:
Reinsurance ceded	44	348	160
Policyholder benefits and claims:
Reinsurance ceded	(420)	(737)	(656)
Affiliated Entity [Member] | Reinsurance [Member]
Premiums:
Net premiums	(524)	(731)	(460)
Universal life and investment-type product policy fees:
Net universal life and investment-type product policy fees	89	66	81
Other revenues:
Net other revenues	73	407	162
Policyholder benefits and claims:
Policyholder Benefits and Claims Incurred, Assumed and Ceded	$ (333)	$ (647)	$ (404)