Reinsurance (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Reinsurance (Additional Textual) [Abstract]
Excess of loss reinsured under an agreement	$ 1.0
Reinsurance (Textual) [Abstract]
Percentage of share in results of pooled business subsidiary	80.00%
Percentage of share in results of pooled business owned by third party	20.00%
Quota share reinsurance percentage		50.00%
Donegal Mutual [Member]
Reinsurance (Additional Textual) [Abstract]
Portion of premiums and losses related to personal lines products	100.00%
Minimum [Member]
Reinsurance (Additional Textual) [Abstract]
Percentage of accumulation of losses	90.00%
Maximum amount of loss coverage under reinsurance agreement of property catastrophe	130.0
Quota share reinsurance reduced percentage	40.00%
Maximum [Member]
Reinsurance (Additional Textual) [Abstract]
Percentage of accumulation of losses	100.00%
Maximum amount of loss coverage under reinsurance agreement of property catastrophe	145.0
Quota share reinsurance reduced percentage	50.00%
Catastrophe Reinsurance [Member]
Reinsurance (Additional Textual) [Abstract]
Excess of loss reinsured under an agreement	$ 5.0