Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2021	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss) attributable to Myriad Genetics, Inc. stockholders	$ (53.1)	$ (27.2)	$ (199.5)	$ 4.6
Unrealized gain (loss) on available-for-sale securities, net of tax	(0.5)	(1.0)	0.7	1.2
Change in pension liability	0.0	0.0	0.0	0.6
Change in foreign currency translation adjustment, net of tax	3.4	(1.8)	(0.6)	(3.1)
Comprehensive income (loss)	$ (50.2)	$ (30.0)	$ (199.4)	$ 3.3