Benefit Plans (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage	50.00%
Director Compensation Expenses	$ 205	$ 144
Defined Contribution Plan, Employer Matching Contribution, Description	The Company has a 401(k) plan established for substantially all full-time employees, as defined. Employee contributions are limited to the maximum established by the Internal Revenue Service on an annual basis. The Company has elected to match contributions equal to 100% of the first 1% of employee deferrals and then 50% on deferrals over 1% up to a maximum of 6% of an individuals total eligible salary, as defined by the plan.
Defined Contribution Plan, Employer Discretionary Contribution Amount	252	214
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total	773
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years
Equity Incentive Plan 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	595,500
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	750,000
Allocated Share-based Compensation Expense	387
Stock Option Plan 2006 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		0
Deferred Stock Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Director Compensation Expenses	$ 127	$ 95
Directors Deferred Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock Shares Reserved For Future Issuance	180,000
Directors Deferred Stock Plan, Percentage	100.00%

Represents the total number of common stock shares which can be issued under the plan.

No definition available.

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Period Type:	duration

- Definition

The description of employer matching contribution under defined contribution plan.

+ References

No definition available.

+ Details

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- Definition

It represents compensation paid to director during the reporting period.

+ References

No definition available.

+ Details

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Namespace Prefix:	inbk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the percentage of directors annual retention in either common stock or deferred stock rights under directors deferred stock plan.

+ References

No definition available.

+ Details

Name:	inbk_DirectorsDeferredStockPlanPercentage
Namespace Prefix:	inbk_
Data Type:	num:percentItemType
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Period Type:	duration

- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 14.F)

-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(1)(i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

+ References

No definition available.

+ Details

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

- Definition

Percentage of employer's matching contributions to a defined contribution plan that vests in a given year.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant