Fathom OpCo Predecessor Period Acquisitions - Summit and PPC - Summary of Total Purchase Consideration Transferred (Details) - USD ($) $ in Thousands	Apr. 30, 2021	Feb. 01, 2021
P P C [Member]
Business Acquisition [Line Items]
Cash	$ 25,721
Fair value of total consideration transferred	$ 25,721
Summit [Member]
Business Acquisition [Line Items]
Cash		$ 10,875
Fair value of total consideration transferred		$ 10,875

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=126966197&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126975305&loc=d3e6927-128479

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126966197&loc=d3e6578-128477

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration