Concentrations of Credit Risk (Details)	Dec. 31, 2019 Institution
Concentrations of Credit Risk [Abstract]
Number of financial institutions with which accounts are maintained in excess of the amount insured by FDIC	4

The number of financial institutions with which the cash and cash equivalents are maintained, as of the balance sheet date that is not insured by the Federal Deposit Insurance Corporation.

No definition available.

Name:	hall_NumberOfFinancialInstitutions
Namespace Prefix:	hall_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant