Investments (Schedule of Securities Pledged by Contractual Maturity) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Lending	$ 161	$ 114
Corporate Bonds [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Lending	160	114
Foreign Government Bonds [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Lending	1
Overnight and Continuous [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Lending	161	114
Overnight and Continuous [Member] | Corporate Bonds [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Lending	160	$ 114
Overnight and Continuous [Member] | Foreign Government Bonds [Member]
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Lending	$ 1