Borrowed Funds - Summary of Federal Home Loan Bank Advances and Securities Sold Under Agreements to Repurchase (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Average balance	$ 382,464	$ 258,870
Maximum amount outstanding at any month end	$ 675,802	$ 291,615
Average interest rate for the year	2.06%	1.73%
Reverse Repurchase Agreements
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Average balance	$ 66,340	$ 74,712
Maximum amount outstanding at any month end	$ 82,463	$ 80,945
Average interest rate for the year	0.25%	0.16%
Amortized cost of collateral, Mortgage-backed securities	$ 75,425	$ 58,020
Estimated fair value of collateral, Mortgage-backed securities	$ 74,144	$ 58,007

Amortized Cost Of Collateral Pledged

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- Definition

Debt Instrument Monthly Maximum Amount Outstanding

+ References

No definition available.

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- Definition

Long Term Debt Average Outstanding Amount

+ References

No definition available.

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- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

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- Definition

The calculated average balance outstanding for the year for all Federal Home Loan Bank advances as of the Balance Sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

The calculated weighted average interest rate for Federal Home Loan Bank advances for the period ended as of the Balance Sheet date.

+ References

+ Details

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- Definition

The maximum balance outstanding at any month end during the period as of the Balance Sheet date.

+ References

+ Details

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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.

+ References

No definition available.

+ Details

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- Definition

The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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