Investments - Summary of Financial Information (Detail) (Donegal Financial Services Corporation [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Donegal Financial Services Corporation [Member]
Balance sheets:
Total assets	$ 510,549		$ 510,549		$ 512,578
Total liabilities	430,084		430,084		438,649
Stockholders' equity	80,465		80,465		73,929
Total liabilities and stockholders' equity	510,549		510,549		512,578
Income statements:
Net income	$ 989	$ 1,525	$ 2,561	$ 5,184