Deposits - Schedule of Interest Expense on Deposits (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Banking and Thrift [Abstract]
Savings	$ 13.4	$ 7.2	$ 9.7
Interest-bearing checking and money market	195.9	120.2	70.4
Time	147.6	88.7	50.6
Total	$ 356.9	$ 216.1	$ 130.7

Interest expense incurred on all checking and money market deposits.

No definition available.

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Namespace Prefix:	pbct_
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Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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- Definition

Aggregate amount of interest expense on all deposits.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.6)
-URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260

+ Details

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- Definition

Interest expense incurred on all savings account deposits.

+ References

+ Details

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- Definition

The aggregate interest expense incurred on time deposits, including certificates of deposits, in domestic offices.

+ References

+ Details

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