Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Jun. 30, 2012
Basis of Presentation (Textual) [Abstract]
Reclassified retained earnings related to an immaterial error	$ 1.8

Reclassified retained earnings related to an immaterial error.

No definition available.

Name:	dgica_ReclassifiedRetainedEarningsRelatedToImmaterialError
Namespace Prefix:	dgica_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration