Business Developments And Risks And Uncertainties (Narrative) (Detail) $ in Millions	9 Months Ended
Sep. 30, 2020 USD ($) segments	Jun. 17, 2019 USD ($)
Business Acquisition [Line Items]
Number of operating segments \| segments	3
Federal legislation passed to combat the economic impact	$ 2,700,000
GO And PBA Bonds [Member] \| Plan support agreement [Member]
Business Acquisition [Line Items]
Debt And Unsecured Claims Outstanding		$ 35,000
Puerto Rico [Member]
Business Acquisition [Line Items]
Claims payments	391
Outstanding bonds	$ 2,900

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599

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