Benefit Plans (Narrative) (Details) - Pension Plan - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Insurance Claims and Policyholder's Benefits, Including Policyholder's Dividends
Net periodic defined benefits expense (reversal of expense), excluding service cost component	$ 3	$ 2
Other Expense
Net periodic defined benefits expense (reversal of expense), excluding service cost component	$ 8	$ 5

Amount of expense (reversal of expense) for net periodic benefit cost components, excluding service cost component, of defined benefit plan. Amount includes, but is not limited to, interest cost, expected (return) loss on plan asset, amortization of prior service cost (credit), amortization of (gain) loss, amortization of transition (asset) obligation, settlement (gain) loss, curtailment (gain) loss and certain termination benefits.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 3A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919

Name:	us-gaap_NetPeriodicDefinedBenefitsExpenseReversalOfExpenseExcludingServiceCostComponent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration