Significant Accounting Policies (Policies)	9 Months Ended
Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The condensed consolidated financial statements included herein have been prepared by AmerInst Insurance Group, Ltd. (“AmerInst”) without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “Commission”). These financial statements reflect all adjustments consisting of normal recurring accruals, which are, in the opinion of management, necessary for a fair presentation of our financial position and results of operations as of the end of and for the periods presented in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). All intercompany transactions and balances have been eliminated on consolidation. These statements are condensed and do not incorporate all the information required under U.S. GAAP to be included in a full set of financial statements. In these notes, the terms “we”, “us”, “our” or the “Company” refer to AmerInst and its subsidiaries. These condensed statements should be read in conjunction with the audited consolidated financial statements at and for the year ended December 31, 2017 and notes thereto, included in AmerInst’s Annual Report on Form 10 -K for the year then ended.
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Pronouncements New Accounting Standards Adopted in 2018 Revenue from Contracts with Customers In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU 2014 - 09, “Revenue from Contracts with Customers. ASU 2014 - 09 provided a framework, through a five -step process, for recognizing revenue from customers, improves comparability and consistency of recognizing revenue across entities, industries, jurisdictions and capital markets, and requires enhanced disclosures. Certain contracts with customers are specifically excluded from the scope of ASU 2014 - 09, including; without limitation, insurance contracts accounted for under Accounting Standard Codification 944, Financial Services—Insurance. ASU 2014 - 09 was effective for annual reporting periods beginning after December 15, 2017 with retrospective adoption required for the comparative periods. The adoption of ASU 2014 - 09 did not have a material impact on the Company’s consolidated financial statements. Classification of Certain Cash Receipts and Cash Payments In August 2016, the FASB issued ASU 2016 - 15, “Statement of Cash Flows (Topic 230 )—Classification of Certain Cash Receipts and Cash Payments” which addressed diversity in practice in how eight specific cash receipts and cash payments should be presented and classified on the statement of cash flows. This guidance was effective for interim and annual periods beginning after December 15, 2017, with early adoption permitted. As this guidance relates solely to financial statement disclosures, the adoption of ASU 2016 - 15, did not impact the Company’s results of operations, financial condition and liquidity. Statement of Cash Flows—Restricted Cash In November 2016, the FASB issued ASU 2016 - 18, which required that a statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. This ASU was effective for periods beginning after December 15, 2017. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU Update 2016 - 01, “Financial Instruments—Overall (Subtopic 825 - 10 ): Recognition and Measurement of Financial Assets and Financial Liabilities. ASU 2016 - 01 changed current U.S. GAAP for public entities by requiring the following, among others: ( 1 ) equity securities, except those accounted for under the equity method of accounting, to be measured at fair value with changes in fair value recognized in net income; ( 2 ) the use of the exit price when measuring fair value of financial instruments for disclosure purposes; ( 3 ) an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value; and ( 4 ) separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or notes to the financial statements. ASU 2016 - 01 was effective for annual periods beginning after December 15, 2017, including interim periods. Early application was permitted. We adopted ASU 2016 - 01 on January 1, 2018. As a result, we recorded a cumulative-effect adjustment to increase beginning retained earnings by $5.1 million, representing the unrealized appreciation on our equity investments with an offsetting adjustment to decrease accumulated other comprehensive income. All subsequent changes in fair value of our equity investments are recognized within realized and unrealized gains (losses) on the consolidated statement of operations. Prior period amounts have not been adjusted and continue to be reported in accordance with the previous accounting guidance. Accounting Standards Not Yet Adopted Financial Instruments Credit Losses-Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU 2016 - 13, which amends the guidance on impairment of financial instruments and significantly changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The ASU will replace the existing “incurred loss” approach, with an “expected loss” model for instruments measured at amortized cost and require entities to record allowances for available-for-sale debt securities rather than reduce the carrying amount under the existing other-than temporary-impairment model. The ASU also simplifies the accounting model for purchased credit-impaired debt securities and loans. The ASU is effective for interim and annual reporting periods beginning after December 15, 2019. We are evaluating the impact of the adoption of this ASU, but we do not currently expect that adoption of this ASU will likely have a material impact on our consolidated financial statements. Test for Goodwill Impairment In January 2017, the FASB issued ASU 2017 - 04, which simplifies the accounting for goodwill impairments by eliminating Step 2 from the goodwill impairment test. Instead, if the carrying amount of a reporting unit exceeds its fair value, an impairment loss shall be recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. The ASU is effective for any interim and annual impairment tests for periods beginning after December 15, 2019. Early adoption is permitted for any interim and annual impairment tests occurring after January 1, 2017. We do not expect the adoption of this ASU to have a material impact on our consolidated financial statements. Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income In February 2018, the FASB issued ASU 2018 - 02 “Income Statement—Reporting Comprehensive Income (Topic 220 )—Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” in response to a financial reporting issue that arose as a consequence of the U.S. federal government tax bill, H.R.1, An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018 (“U.S. Tax Reform”) which became law on December 22, 2017. U.S. GAAP currently requires deferred tax liabilities and assets to be adjusted for the effect of a change in tax laws or rates with the effect included in income from continuing operations in the reporting period that includes the enactment date. This guidance is applicable even in situations in which the related income tax effects of items in accumulated other comprehensive income were originally recognized in other comprehensive income rather than in income from continuing operations. As the adjustment of deferred taxes due to the reduction of the historical corporate income tax rate to the newly enacted corporate income tax rate is required to be included in income from continuing operations, the tax effects of items within accumulated other comprehensive income (referred to as stranded tax effects for purposes of this Update) do not reflect the appropriate tax rate. The amendments in this update allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from U.S. Tax Reform. Consequently, the amendments eliminate the stranded tax effects resulting from U.S. Tax Reform and will improve the usefulness of information reported to financial statement users. However, because the amendments only relate to the reclassification of the income tax effects of U.S. Tax Reform, the underlying guidance that requires the effect of a change in tax laws or rates be included in income from continuing operations is not affected.

New Accounting Pronouncements

New Accounting Standards Adopted in

2018

Revenue from Contracts with Customers

May 2014,

the Financial Accounting Standards Board (“FASB”) issued ASU

2014

09,

“Revenue from Contracts with Customers. ASU

2014

provided a framework, through a

five

-step process, for recognizing revenue from customers, improves comparability and consistency of recognizing revenue across entities, industries, jurisdictions and capital markets, and requires enhanced disclosures. Certain contracts with customers are specifically excluded from the scope of ASU

2014

09,

including; without limitation, insurance contracts accounted for under Accounting Standard Codification

944,

Financial Services—Insurance. ASU

2014

was effective for annual reporting periods beginning after

December

15,

2017

with retrospective adoption required for the comparative periods. The adoption of ASU

2014

did

not

have a material impact on the Company’s consolidated financial statements.

Classification of Certain Cash Receipts and Cash Payments

August 2016,

the FASB issued ASU

2016

15,

“Statement of Cash Flows (Topic

230

)—Classification of Certain Cash Receipts and Cash Payments” which addressed diversity in practice in how

eight

specific cash receipts and cash payments should be presented and classified on the statement of cash flows. This guidance was effective for interim and annual periods beginning after

December

15,

2017,

with early adoption permitted. As this guidance relates solely to financial statement disclosures, the adoption of ASU

2016

15,

did

not

impact the Company’s results of operations, financial condition and liquidity.

Statement of Cash Flows—Restricted Cash

November 2016,

the FASB issued ASU

2016

18,

which required that a statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. This ASU was effective for periods beginning after

December

15,

2017.

Recognition and Measurement of Financial Assets and Financial Liabilities

January 2016,

the FASB issued ASU Update

2016

01,

“Financial Instruments—Overall (Subtopic

825

): Recognition and Measurement of Financial Assets and Financial Liabilities. ASU

2016

changed current U.S. GAAP for public entities by requiring the following, among others: (

) equity securities, except those accounted for under the equity method of accounting, to be measured at fair value with changes in fair value recognized in net income; (

) the use of the exit price when measuring fair value of financial instruments for disclosure purposes; (

) an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value; and (

) separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or notes to the financial statements. ASU

2016

was effective for annual periods beginning after

December

15,

2017,

including interim periods. Early application was permitted.

We adopted ASU

2016

January

2018.

As a result, we recorded a cumulative-effect adjustment to increase beginning retained earnings by

$5.1

million, representing the unrealized appreciation on our equity investments with an offsetting adjustment to decrease accumulated other comprehensive income. All subsequent changes in fair value of our equity investments are recognized within realized and unrealized gains (losses) on the consolidated statement of operations. Prior period amounts have

not

been adjusted and continue to be reported in accordance with the previous accounting guidance.

Accounting Standards

Not

Yet Adopted

Financial Instruments Credit Losses-Measurement of Credit Losses on Financial Instruments

June 2016,

the FASB issued ASU

2016

13,

which amends the guidance on impairment of financial instruments and significantly changes how entities will measure credit losses for most financial assets and certain other instruments that are

not

measured at fair value through net income. The ASU will replace the existing “incurred loss” approach, with an “expected loss” model for instruments measured at amortized cost and require entities to record allowances for available-for-sale debt securities rather than reduce the carrying amount under the existing other-than temporary-impairment model. The ASU also simplifies the accounting model for purchased credit-impaired debt securities and loans. The ASU is effective for interim and annual reporting periods beginning after

December

15,

2019.

We are evaluating the impact of the adoption of this ASU, but we do

not

currently expect that adoption of this ASU will likely have a material impact on our consolidated financial statements.

Test for Goodwill Impairment

January 2017,

the FASB issued ASU

2017

04,

which simplifies the accounting for goodwill impairments by eliminating Step

from the goodwill impairment test. Instead, if the carrying amount of a reporting unit exceeds its fair value, an impairment loss shall be recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. The ASU is effective for any interim and annual impairment tests for periods beginning after

December

15,

2019.

Early adoption is permitted for any interim and annual impairment tests occurring after

January

2017.

We do

not

expect the adoption of this ASU to have a material impact on our consolidated financial statements.

Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income

February 2018,

the FASB issued ASU

2018

“Income Statement—Reporting Comprehensive Income (Topic

220

)—Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” in response to a financial reporting issue that arose as a consequence of the U.S. federal government tax bill,

H.R.1,

An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year

2018

(“U.S. Tax Reform”) which became law on

December

22,

2017.

U.S. GAAP currently requires deferred tax liabilities and assets to be adjusted for the effect of a change in tax laws or rates with the effect included in income from continuing operations in the reporting period that includes the enactment date. This guidance is applicable even in situations in which the related income tax effects of items in accumulated other comprehensive income were originally recognized in other comprehensive income rather than in income from continuing operations. As the adjustment of deferred taxes due to the reduction of the historical corporate income tax rate to the newly enacted corporate income tax rate is required to be included in income from continuing operations, the tax effects of items within accumulated other comprehensive income (referred to as stranded tax effects for purposes of this Update) do

not

reflect the appropriate tax rate.

The amendments in this update allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from U.S. Tax Reform. Consequently, the amendments eliminate the stranded tax effects resulting from U.S. Tax Reform and will improve the usefulness of information reported to financial statement users. However, because the amendments only relate to the reclassification of the income tax effects of U.S. Tax Reform, the underlying guidance that requires the effect of a change in tax laws or rates be included in income from continuing operations is

not

affected.