Investments - Additional Information (Detail) (U.S. non-qualified deferred compensation plan [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
U.S. non-qualified deferred compensation plan [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Aggregate cost basis for investments	$ 9.9	$ 9.3

Aggregate cost basis for non qualified deferred compensation plan.

No definition available.

Name:	hsii_AggregateCostBasisForNonQualifiedDeferredCompensationPlan
Namespace Prefix:	hsii_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant