Document And Entity Information - USD ($)	5 Months Ended
	Dec. 31, 2020	Mar. 29, 2021
Document Information Line Items
Entity Registrant Name	Motion Acquisition Corp.
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Public Float	$ 0
Amendment Flag	false
Entity Central Index Key	0001822359
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Shell Company	true
Entity Ex Transition Period	false
Entity Incorporation, State or Country Code	DE
Entity File Number	001-39618
Document Transition Report	false
Entity Interactive Data Current	Yes
Class A Common Stock
Document Information Line Items
Entity Common Stock, Shares Outstanding		11,500,000
Class B Common Stock
Document Information Line Items
Entity Common Stock, Shares Outstanding		2,875,000