Fair Value of Financial Instruments (Details Textual) (Level 3 [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Level 3 [Member]
Fair Value of Financial Instruments (Textual) [Abstract]
Percentage of investment portfolio fair value	89.00%
Unrealized gain or losses	$ 4,590	$ 0
Percentage of invested assets in whole investment portfolio	3.00%

Realized gain loss on assets included in earning due to change in unrealized gain or losses attributable to Level 3 assets still held.

No definition available.

Name:	hmn_RealizedGainLossOnAssetsIncludedInEarningsDueToChangeInUnrealizedGainOrLossesLevelThree
Namespace Prefix:	hmn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant