Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
LIBOR period	3 months
Weighted average fixed rate	5.81%
Recorded period of effectiveness of cash flow hedges on net income	12 months
Recorded period of effectiveness of fair value hedges on net income	12 months
Recorded period of effectiveness of fair value of derivatives on net income	12 months
LaPorte Bancorp Inc [Member]
Derivative [Line Items]
LIBOR period	1 month
Weighted average fixed rate	2.31%
Cash Flow Hedging [Member]
Derivative [Line Items]
Notional amount of interest	$ 30.5	$ 30.5
Cash Flow Hedging [Member] \| LaPorte Bancorp Inc [Member]
Derivative [Line Items]
Notional amount of interest	30.0	30.0
Derivative in Fair Value Hedging Relationship [Member]
Derivative [Line Items]
Notional amount of interest	$ 155.0	$ 154.6

Cash flow hedge derivatives expected period of insignificant impact on net income.

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- Definition

Fair flow hedge derivatives expected period of insignificant impact on net income.

+ References

No definition available.

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- Definition

LIBOR period.

+ References

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- Definition

Non designated hedge derivatives expected period of insignificant impact on net income.

+ References

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- Definition

Nominal or face amount used to calculate payments on the derivative asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959

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- Definition

Average fixed interest rate related to the group of interest rate derivatives.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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