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New Accounting Standards (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease ROU asset		$ 233
Operating lease liability		$ 240
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease ROU asset			$ 207
Operating lease liability			$ 214
Accounting Standards Update 2019-05 [Member] \| Forecast [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption	$ 14