Income Tax (Net Deferred Income Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets:
Policyholder liabilities and receivables	$ 2,654	$ 2,029
Net operating loss carryforwards	512	1,420
Employee benefits	802	1,045
Capital loss carryforwards	6	9
Tax credit carryforwards	1,322	1,375
Litigation-related and government mandated	160	268
Other	657	743
Total gross deferred income tax assets	6,113	6,889
Less: Valuation allowance	189	161
Total net deferred income tax assets	5,924	6,728
Deferred income tax liabilities:
Investments, including derivatives	2,772	2,940
Intangibles	1,321	1,213
Net unrealized investment gains	4,783	5,423
DAC	3,206	3,619
Other	609	425
Total deferred income tax liabilities	12,691	13,620
Deferred tax assets and liabilities [Abstract]
Net deferred income tax asset (liability)	$ (6,767)	$ (6,892)