Fair Value of Financial Instruments (Details Textual) (Level 3 [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Level 3 [Member]
Fair Value of Financial Instruments (Textual) [Abstract]
Percentage of investment portfolio fair value	88.00%	91.00%
Percentage of invested assets in whole investment portfolio	1.80%
Net realized gains or losses	$ 0	$ 0

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