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	$ 39,595	$ 37,975	$ 37,044
Reinsurance assumed	1,773	1,363	1,382
Reinsurance ceded	(2,376)	(2,136)	(2,023)
Net premiums	38,992	37,202	36,403
Universal life and investment-type product policy fees:
Direct universal life and investment-type product policy fees	5,978	5,884	5,952
Reinsurance assumed	83	96	105
Reinsurance ceded	(551)	(497)	(487)
Net universal life and investment product policy fees	5,510	5,483	5,570
Policyholder Benefits and Claims:
Direct policyholder benefits and claims	39,354	37,186	36,143
Reinsurance assumed	1,388	1,085	984
Reinsurance ceded	(2,429)	(1,913)	(1,983)
Net policyholder benefits and claims	38,313	36,358	35,144
Other expenses:
Direct other expenses	13,610	13,958	14,934
Reinsurance assumed	246	169	146
Reinsurance ceded	235	378	303
Total other expenses	$ 13,621	$ 13,749	$ 14,777