Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (59.3)	$ (54.0)	$ (78.3)	$ (94.7)
Foreign currency translation, net of tax	(45.7)	6.1	(61.4)	(12.0)
Unrecognized actuarial gain and prior service benefit, net of tax	0.1	0.5	0.1	0.7
Other comprehensive (loss) income, net of tax	(45.6)	6.6	(61.3)	(11.3)
Comprehensive loss	(104.9)	(47.4)	(139.6)	(106.0)
Less: Comprehensive loss attributable to noncontrolling interest	(2.5)	(0.1)	(5.3)	(0.1)
Comprehensive loss attributable to Mirion Technologies, Inc. (Successor) / Mirion Technologies (TopCo), Ltd. (Predecessor) stockholders	$ (102.4)	$ (47.3)	$ (134.3)	$ (105.9)