Derivatives (Changes in Estimated Fair Value Related to Embedded Derivatives) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Net derivative gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives gains (losses)	$ (231)	$ 552
Policyholder benefits and claims
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives gains (losses)	$ 0	$ (1)

Net Increase or Decrease in the fair value of the embedded derivative or group of embedded derivatives included in earnings in the period.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 15
-URI http://asc.fasb.org/subtopic&trid=2229187

Name:	us-gaap_EmbeddedDerivativeGainLossOnEmbeddedDerivativeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration