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Contingent Consideration From Sale Of Business.

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Percentage of share in results of pooled business owned by third party.

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Percentage of share in results of pooled business subsidiary.

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Percentage of voting power owned by major shareholder.

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Stock ownership percentage held by major shareholder.

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Stock ownership percentage owned by third party.

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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.

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Carrying amount as of the balance sheet date of dividends declared but not received.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Date the operations of the entity commenced, in CCYY-MM-DD format.

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Dividends received on equity and other investments during the current period.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Organization - Additional Information (Detail) $ in Millions		6 Months Ended	59 Months Ended
	Jun. 11, 2018 USD ($)	Jun. 30, 2018 USD ($) Segment	Jun. 30, 2018 shares	Jul. 18, 2013 shares
Business Acquisition [Line Items]
Operations commenced date		Aug. 26, 1986
Stock ownership percentage owned by third party		51.80%
Number of operating segments \| Segment		4
Voting power percentage of outstanding common stock		72.00%
Restructuring charge for employee termination costs		$ 1.9
Atlantic States [Member]
Business Acquisition [Line Items]
Percentage of share in results of pooled business subsidiary		80.00%
Donegal Mutual [Member]
Business Acquisition [Line Items]
Percentage of share in results of pooled business owned by third party		20.00%
DFSC and North West [Member] \| Donegal Mutual Insurance Company [Member]
Business Acquisition [Line Items]
Consideration from sale of business	$ 85.0
Proceeds from dividend	$ 30.0
Donegal Financial Services Corporation [Member]
Business Acquisition [Line Items]
Outstanding stock ownership percentage		48.20%	48.20%
Donegal Financial Services Corporation [Member] \| DFSC and North West [Member]
Business Acquisition [Line Items]
Outstanding stock ownership percentage	48.20%
Dividend payment to be received	$ 14.5
Donegal Financial Services Corporation [Member] \| DFSC and North West [Member] \| Minimum [Member]
Business Acquisition [Line Items]
Consideration from sale of business and dividend	38.9
Donegal Financial Services Corporation [Member] \| DFSC and North West [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Consideration from sale of business and dividend	$ 43.0
Class A Common Stock [Member]
Business Acquisition [Line Items]
Stock ownership percentage held by major shareholder		43.00%
Class A Common Stock [Member] \| Stock Repurchase Program Two [Member]
Business Acquisition [Line Items]
Authority to purchase shares \| shares				500,000
Common stock shares purchased \| shares			57,658
Class B Common Stock [Member]
Business Acquisition [Line Items]
Stock ownership percentage held by major shareholder		84.00%