Loans and the Allowance for Loan Losses - Summary of Informative Data Regarding Loan Modifications (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2015 USD ($) Contracts	Dec. 31, 2014 USD ($) Contracts
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contracts	11	19
Pre-Modification Outstanding Recorded Investment	$ 8,447	$ 14,333
Post-Modification Outstanding Recorded Investment	$ 5,865	$ 9,887
1-4 Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contracts	5	5
Pre-Modification Outstanding Recorded Investment	$ 1,568	$ 1,519
Post-Modification Outstanding Recorded Investment	$ 1,008	$ 973
Nonfarm Nonresidential [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contracts	3	5
Pre-Modification Outstanding Recorded Investment	$ 5,143	$ 7,201
Post-Modification Outstanding Recorded Investment	$ 3,623	$ 4,047
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contracts	3	6
Pre-Modification Outstanding Recorded Investment	$ 1,736	$ 3,888
Post-Modification Outstanding Recorded Investment	$ 1,234	$ 3,658
Construction and Land [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contracts		1
Pre-Modification Outstanding Recorded Investment		$ 1,586
Post-Modification Outstanding Recorded Investment		$ 1,162
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts \| Contracts		2
Pre-Modification Outstanding Recorded Investment		$ 139
Post-Modification Outstanding Recorded Investment		$ 47

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.

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ck0001624322_ResidentialOneToFourFamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ck0001624322_NonFarmNonresidentialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ck0001624322_ConstructionAndLandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: