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Transactions with Affiliates - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Ceded Credit Risk [Line Items] |  |  |  |
Premiums and losses related to certain products | 63.50% | 63.90% | 64.30% |
Coverage under catastrophic occurrence |  |  |  | $ 1,500,000
Charges for services |  | $ 134,143,158 | $ 126,153,511 | 124,999,770
Maximum [Member] | Lease Office Equipment And Automobile [Member] |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Lease office equipment and automobiles range |  | 10 years |  |
Minimum [Member] | Lease Office Equipment And Automobile [Member] |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Lease office equipment and automobiles range |  | 3 years |  |
Atlantic States [Member] |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Percentage of share in results of pooled business subsidiary | 80.00% | 80.00% |  |
Coverage under catastrophic occurrence |  | $ 2,500,000 | 2,000,000 | 2,000,000
Donegal Mutual [Member] |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Percentage of share in results of pooled business owned by third party | 20.00% | 20.00% |  |
Premiums and losses related to certain products | 100.00% |  |  |
Premiums and losses related to business of MICO |  | 25.00% |  |
Coverage under catastrophic occurrence | $ 2,000,000 |  |  |
Excess of loss reinsured under an agreement |  | $ 500,000 |  |
Period of Donegal Mutual under lease agreement |  | 10 years |  |
Le Mars [Member] |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Coverage under catastrophic occurrence |  | $ 1,000,000 | 750,000 | $ 750,000
Southern [Member] |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Premiums and losses related to certain products |  | 100.00% |  |
Coverage under catastrophic occurrence |  | $ 2,000,000 | $ 1,500,000 |
Excess of loss reinsured under an agreement |  | 500,000 |  |
Insurance Subsidiaries [Member] |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Coverage under catastrophic occurrence | $ 5,000,000 | 5,000,000 |  |
Excess of loss reinsured under an agreement |  | $ 5,000,000 |  |

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- Definition The expense incurred by an insurance company to persons or entities for generating or placing insurance or investment contracts with the company, usually determined as a percentage of policy or contract premiums. Excludes advances or draws to be applied against commissions earned. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.7(a)) -URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263 + Details
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