Investments - Summary of Financial Information (Detail) (Donegal Financial Services Corporation [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Donegal Financial Services Corporation [Member]
Balance sheets:
Total assets	$ 519,366		$ 519,366		$ 512,578
Total liabilities	439,906		439,906		438,649
Stockholders' equity	79,460		79,460		73,929
Total liabilities and stockholders' equity	519,366		519,366		512,578
Income statements:
Net income	$ 723	$ 1,401	$ 1,572	$ 3,659