Summary of Significant Accounting Policies - Revenue Recognition (Details)	9 Months Ended
Sep. 30, 2021
Summary of Significant Accounting Policies
Notice in days for cancellation of contract	30 days

The notice period for cancellation of contract, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	fthm_NoticePeriodForCancellationOfContract
Namespace Prefix:	fthm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration