Variable Interest Entities (Consolidated Variable Interest Entity Asset and Liability Information) (Details) $ in Millions	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($) item
Disclosure Of Variable Interest Entities Assets And Liabilities [Line Items]
Number of Instruments | item	1	1
Notional Amounts | $	$ 613	$ 600
Total Return Swap [Member]
Disclosure Of Variable Interest Entities Assets And Liabilities [Line Items]
Number of Instruments | item	1	1
Notional Amounts | $	$ 613	$ 600