Investments (Invested Assets On Deposit, Held in Trust and Pledged as Collateral - Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Invested assets on deposit (regulatory deposits)	$ 9,439	$ 8,172
Invested assets held in trust (reinsurance agreements)	4,429	3,455
Fixed maturity securities \| Policyholder account balances
Invested assets on deposit (regulatory deposits)	75	55
Fixed maturity securities \| Reinsurance
Invested assets held in trust (reinsurance agreements)	$ 132	$ 87

The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(b))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Name:	us-gaap_AssetsHeldInTrust
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant