Cover Page - shares	Jun. 30, 2020	Sep. 30, 2020
Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Registrant Name	dMY Technology Group, Inc. II
Entity Central Index Key	0001816101
Current Fiscal Year End Date	--12-31
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Entity File Number	001-39444
Entity Tax Identification Number	84-1502857
Entity Address, Address Line One	1180 North Town Center Drive
Entity Address, Address Line Two	Suite 100
Entity Address, City or Town	Las Vegas
Entity Address, State or Province	NV
Entity Address, Postal Zip Code	89144
City Area Code	702
Local Phone Number	781-4313
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Shell Company	true
Entity Ex Transition Period	false
Capital Units [Member]
Entity Information [Line Items]
Trading Symbol	DMYD.U
Title of 12(b) Security	Units, each consisting of one share of Class A common stock and one-third of one redeemable warrant
Security Exchange Name	NYSE
Common Class A [Member]
Entity Information [Line Items]
Trading Symbol	DMYD
Title of 12(b) Security	Class A common stock, par value $0.0001 per share
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		27,600,000
Warrant [Member]
Entity Information [Line Items]
Trading Symbol	DMYD
Title of 12(b) Security	Warrants, each whole warrant exercisable for one share of Class A common stock, each at an exercise price of $11.50 per share
Security Exchange Name	NYSE
Common Class B [Member]
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		6,900,000