Deferred Policy Acquisition Costs, Value of Business Acquired and Other Policy-Related Intangibles (DAC and VOBA) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net [Abstract]
Present Value of Future Insurance Profits, Amortization Expense, Realized Gain (Loss)	$ (9)	$ 2	$ (19)
Beginning Balance of DAC	5,667	5,066	5,097
Capitalizations of DAC	256	330	399
Net investment gains (losses) of DAC and net derivative gains (losses) of DAC	127	1,371	163
Other expenses of DAC	(958)	(1,076)	(690)
Total amortization of DAC	(831)	295	(527)
Unrealized investment gains (losses) of DAC	(77)	(24)	97
Ending Balance of DAC	5,015	5,667	5,066
Beginning Balance of VOBA	672	711	763
Other expenses of VOBA	(76)	(72)	(127)
Total amortization of VOBA	(85)	(70)	(146)
Unrealized investment gains (losses) of VOBA	21	31	94
Ending Balance of VOBA	608	672	711
Balance at December 31,	$ 5,623	$ 6,339	$ 5,777