Condensed Financial Information of Parent Company - Summary of Condensed Statements of Cash Flows (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities:
Net income (loss)	$ 47,151,744	$ (32,760,340)	$ 7,116,100
Adjustments:
Realized investment gains	(21,984,617)	4,801,509	(5,705,255)
Other	6,033,243	299,262	(113,482)
Net adjustments	29,208,033	96,536,474	73,884,098
Net cash provided by operating activities	76,359,777	63,776,134	81,000,198
Cash Flows from Investing Activities:
Net (purchases) sale of short-term investments	2,718,538	(5,698,845)	(1,678,908)
Sale of equity securities	20,287,000
Net cash used in investing activities	(43,377,179)	(37,606,007)	(58,443,382)
Cash Flows from Financing Activities:
Cash dividends paid	(16,092,643)	(15,658,950)	(14,822,052)
Issuance of common stock	4,834,514	3,249,849	15,511,457
Payments on lines of credit	(25,000,000)		(10,000,000)
Borrowings under lines of credit		1,000,000
Net cash used in financing activities	(36,258,129)	(11,409,101)	(9,310,595)
Cash at beginning of year	52,594,461	37,833,435	24,587,214
Cash at end of year	49,318,930	52,594,461	37,833,435
Donegal Financial Services Corporation [Member]
Adjustments:
Dividends received from DFSC			1,037,000
Cash Flows from Investing Activities:
Sale of equity securities	33,923,000
Parent Company [Member]
Cash Flows from Operating Activities:
Net income (loss)	47,152,000	(32,760,000)	7,116,000
Adjustments:
Equity in undistributed net (income) loss of subsidiaries	(33,148,000)	42,694,000	5,343,000
Realized investment gains	(12,378,000)
Other	490,000	2,531,000	1,011,000
Net adjustments	(45,036,000)	45,225,000	7,391,000
Net cash provided by operating activities	2,116,000	12,465,000	14,507,000
Cash Flows from Investing Activities:
Net (purchases) sale of short-term investments	(2,473,000)		1,000
Net purchase of property and equipment	(150,000)	(106,000)	(788,000)
Investment in subsidiaries	(18,283,000)	(2,644,000)	(2,992,000)
Other	0	(1,000)	(1,000)
Net cash used in investing activities	33,304,000	(2,751,000)	(3,780,000)
Cash Flows from Financing Activities:
Cash dividends paid	(16,093,000)	(15,659,000)	(14,821,000)
Issuance of common stock	6,481,000	3,250,000	15,511,000
Payments on lines of credit			(10,000,000)
Borrowings under lines of credit		1,000,000
Net cash used in financing activities	(34,612,000)	(11,409,000)	(9,310,000)
Net increase (decrease) in cash	808,000	(1,695,000)	1,417,000
Cash at beginning of year	1,542,000	3,237,000	1,820,000
Cash at end of year	$ 2,350,000	$ 1,542,000	$ 3,237,000