Pension Plans and Other Postretirement Benefits (Details Textual) (USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012
Pension Plans and Other Postretirement Benefits (Textual) [Abstract]
Effective Jan. 1, 2007, minimum age at which previous group health benefits were eliminated	65 years
Health reimbursement accounts funding	$ 132	$ 133
Minimum funding requirement for 2013	$ 0

Effective January 1, 2007, the minimum age at which the Company eliminated the previous group health insurance benefits for retirees, including elimination of pharmacy benefits for Medicare eligible retirees, and established a Health reimbursement Account ("HRA") for each eligible participant.

No definition available.

Name:	hmn_MinimumAgePreviousGroupHealthBenefitsEliminated
Namespace Prefix:	hmn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration