Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss) attributable to Myriad Genetics, Inc. stockholders	$ (8.3)	$ 2.6	$ (28.9)	$ 1.9
Unrealized loss on available-for-sale securities, net of tax	0.0	(0.2)	0.0	(0.4)
Change in foreign currency translation adjustment, net of tax	2.2	0.9	0.1	1.3
Comprehensive income (loss)	(6.1)	3.3	(28.8)	2.8
Comprehensive income attributable to non-controlling interest	0.0	0.0	0.0	0.0
Comprehensive income (loss) attributable to Myriad Genetics, Inc. shareholders	$ (6.1)	$ 3.3	$ (28.8)	$ 2.8