Loans and Allowance for Loan Losses - Summary of Information Regarding Interest Income Recognized on Impaired Loans,by Portfolio (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2021 USD ($)
Average Recorded Investment
With no related allowance recorded:	$ 36,212
With an allowance recorded:	39,345
Total	75,557
Total Interest Recognized
With no related allowance recorded:	280
With an allowance recorded:	159
Total	439
Commercial Portfolio Segment \| Commercial and industrial
Average Recorded Investment
With no related allowance recorded:	9,899
With an allowance recorded:	7,965
Total Interest Recognized
With no related allowance recorded:	46
With an allowance recorded:	0
Commercial Portfolio Segment \| Commercial real estate
Average Recorded Investment
With no related allowance recorded:	4,176
With an allowance recorded:	657
Total Interest Recognized
With no related allowance recorded:	44
With an allowance recorded:	0
Commercial Portfolio Segment \| Business Banking
Average Recorded Investment
With no related allowance recorded:	5,024
With an allowance recorded:	16,325
Total Interest Recognized
With no related allowance recorded:	26
With an allowance recorded:	14
Residential Portfolio Segment \| Residential real estate
Average Recorded Investment
With no related allowance recorded:	14,648
With an allowance recorded:	12,248
Total Interest Recognized
With no related allowance recorded:	144
With an allowance recorded:	127
Consumer Portfolio Segment \| Consumer home equity
Average Recorded Investment
With no related allowance recorded:	2,438
With an allowance recorded:	2,150
Total Interest Recognized
With no related allowance recorded:	20
With an allowance recorded:	18
Consumer Portfolio Segment \| Other Consumer
Average Recorded Investment
With no related allowance recorded:	27
Total Interest Recognized
With no related allowance recorded:	$ 0

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524

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-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5258-111524

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-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5212-111524

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