Commitments and Contingencies (Narrative) (Details) $ in Millions	May 05, 2020 USD ($)
Commitments and Contingencies [Abstract]
Net adverse loss development	$ 63.8

Adverse development loss incurred during the period due to litigation claims filed.

No definition available.

Name:	hall_AdverseDevelopmentLossNet
Namespace Prefix:	hall_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration