XML 52 R42.htm IDEA: XBRL DOCUMENT v3.26.1

Securities - HTM Portfolio Credit Rating (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	$ 264,740	$ 250,710
Standard & Poor's, AAA Rating | Moody's, Aaa Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	237,870	219,165
Standard & Poor's, AA+ Rating | Moody's, Aa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	6,408	7,046
Standard & Poor's, AA Rating | Moody's, Aa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	2,170	2,170
Standard & Poor's, AA- Rating | Moody's, Aa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	1,792	1,793
Standard & Poor's, A- Rating | Moody's, A3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	5,000	5,000
Standard & Poor's, BBB+ Rating | Moody's, Baa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	7,000	5,000
Standard & Poor's, BBB Rating | Moody's, Baa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		4,000
Standard & Poor's, BBB- Rating | Moody's, Baa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	2,500	4,536
Standard & Poor's, BB+ Rating | Moody's, Ba1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		2,000
Standard & Poor's Not Rated | Moody's, Not Rated Agency
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	2,000
Municipal securities
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	10,370	11,009
Municipal securities | Standard & Poor's, AAA Rating | Moody's, Aaa Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Municipal securities | Standard & Poor's, AA+ Rating | Moody's, Aa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	6,408	7,046
Municipal securities | Standard & Poor's, AA Rating | Moody's, Aa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	2,170	2,170
Municipal securities | Standard & Poor's, AA- Rating | Moody's, Aa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	1,792	1,793
Municipal securities | Standard & Poor's, A- Rating | Moody's, A3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Municipal securities | Standard & Poor's, BBB+ Rating | Moody's, Baa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Municipal securities | Standard & Poor's, BBB Rating | Moody's, Baa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		0
Municipal securities | Standard & Poor's, BBB- Rating | Moody's, Baa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Municipal securities | Standard & Poor's, BB+ Rating | Moody's, Ba1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		0
Municipal securities | Standard & Poor's Not Rated | Moody's, Not Rated Agency
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0
Agency mortgage-backed securities - residential
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	232,272	213,530
Agency mortgage-backed securities - residential | Standard & Poor's, AAA Rating | Moody's, Aaa Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	232,272	213,530
Agency mortgage-backed securities - residential | Standard & Poor's, AA+ Rating | Moody's, Aa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - residential | Standard & Poor's, AA Rating | Moody's, Aa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - residential | Standard & Poor's, AA- Rating | Moody's, Aa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - residential | Standard & Poor's, A- Rating | Moody's, A3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - residential | Standard & Poor's, BBB+ Rating | Moody's, Baa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - residential | Standard & Poor's, BBB Rating | Moody's, Baa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		0
Agency mortgage-backed securities - residential | Standard & Poor's, BBB- Rating | Moody's, Baa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - residential | Standard & Poor's, BB+ Rating | Moody's, Ba1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		0
Agency mortgage-backed securities - commercial
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	5,598	5,635
Agency mortgage-backed securities - commercial | Standard & Poor's, AAA Rating | Moody's, Aaa Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	5,598	5,635
Agency mortgage-backed securities - commercial | Standard & Poor's, AA+ Rating | Moody's, Aa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - commercial | Standard & Poor's, AA Rating | Moody's, Aa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - commercial | Standard & Poor's, AA- Rating | Moody's, Aa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - commercial | Standard & Poor's, A- Rating | Moody's, A3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - commercial | Standard & Poor's, BBB+ Rating | Moody's, Baa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - commercial | Standard & Poor's, BBB Rating | Moody's, Baa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		0
Agency mortgage-backed securities - commercial | Standard & Poor's, BBB- Rating | Moody's, Baa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Agency mortgage-backed securities - commercial | Standard & Poor's, BB+ Rating | Moody's, Ba1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		0
Agency mortgage-backed securities - commercial | Standard & Poor's Not Rated | Moody's, Not Rated Agency
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0
Corporate Securities
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	16,500	20,536
Corporate Securities | Standard & Poor's, AAA Rating | Moody's, Aaa Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Corporate Securities | Standard & Poor's, AA+ Rating | Moody's, Aa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Corporate Securities | Standard & Poor's, AA Rating | Moody's, Aa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Corporate Securities | Standard & Poor's, AA- Rating | Moody's, Aa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	0	0
Corporate Securities | Standard & Poor's, A- Rating | Moody's, A3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	5,000	5,000
Corporate Securities | Standard & Poor's, BBB+ Rating | Moody's, Baa1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	7,000	5,000
Corporate Securities | Standard & Poor's, BBB Rating | Moody's, Baa2 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		4,000
Corporate Securities | Standard & Poor's, BBB- Rating | Moody's, Baa3 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	2,500	4,536
Corporate Securities | Standard & Poor's, BB+ Rating | Moody's, Ba1 Rating
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost		$ 2,000
Corporate Securities | Standard & Poor's Not Rated | Moody's, Not Rated Agency
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	2,000
Agency mortgage-backed securities - residential | Standard & Poor's Not Rated | Moody's, Not Rated Agency
Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items]
Held-to-maturity securities, amortized cost	$ 0

X

- 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

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

X

- Definition

Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481962/310-10-50-7A

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-5

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-14

+ Details

Name:	us-gaap_HeldToMaturitySecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsAAARatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysAaaRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsAAPlusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysAa1RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsAARatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysAa2RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsAAMinusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysAa3RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsAMinusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysA3RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsBBBPlusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysBaa1RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsBBBRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysBaa2RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsBBBMinusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysBaa3RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=srt_StandardPoorsBBPlusRatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=srt_MoodysBa1RatingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingStandardPoorsAxis=inbk_StandardPoorsNotRatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CreditRatingMoodysAxis=inbk_MoodysNotRatedAgencyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MunicipalBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_OtherDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: