Segment Reporting (Details Textuals) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020 USD ($)	Mar. 31, 2020	Sep. 30, 2020 USD ($) segment
Segment Reporting [Abstract]
Number of Reportable Segments \| segment			3
Description of Effect on Previously Reported Segment Information for Change in Composition of Reportable Segments		During the first quarter of 2020, the Corporation reassigned goodwill of approximately $4 million to the Corporate and Commercial Specialty segment from the Community, Consumer and Business segment as a result of a reorganization of the investment and fiduciary businesses. The goodwill reassigned was attributable to the Corporation's acquisition of Whitnell & Co. in 2017. Also effective in the first quarter of 2020, the marketing business unit, formerly part of the Risk Management and Shared Services segment, was reorganized under the Community, Consumer and Business segment.
Tax Benefit from Tax Planning Strategies \| $	$ 49		$ 63

Disclosure about a restatement of previous periods' segment information resulting from a change in the composition of the entity's reportable segments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8984-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8981-108599

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