Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended												12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	[1]	Mar. 31, 2018	[1]	Dec. 31, 2017	[1]	Sep. 30, 2017	[1]	Jun. 30, 2019	Jun. 30, 2018	[1]	Jun. 30, 2017	[1]
Total revenue	$ 215.4	$ 216.6	$ 216.8	$ 202.3	$ 193.9		$ 183.1		$ 187.9		$ 178.8		$ 851.1	$ 743.7	[2]	$ 728.7	[2]
Costs and expenses:
Research and development expense	20.9	21.5	22.4	21.1	17.7		18.5		16.8		17.8		85.9	70.8		74.4
Change in the fair value of contingent consideration	(0.3)		1.0	0.4	0.2		(1.2)		13.0		(73.2)		1.1	(61.2)		(0.8)
Selling, general, and administrative expense	149.8	140.6	135.2	129.9	112.5		107.9		107.4		107.2		555.5	435.0		439.9
Total costs and expenses	221.0	210.7	210.7	201.1	176.1		169.3		181.6		94.8		843.5	621.8		684.7
Operating income	(5.6)	5.9	6.1	1.2	17.8		13.8		6.3		84.0		7.6	121.9		44.0
Other income (expense):
Interest income	0.9	0.7	0.9	0.7	0.5		0.5		0.4		0.4		3.2	1.8		1.2
Interest expense	(3.2)	(3.2)	(3.4)	(2.2)	(1.1)		(0.5)		(0.7)		(0.9)		(12.0)	(3.2)		(6.0)
Other	0.2	(0.1)		1.1	0.8		(0.5)		(0.4)		(0.3)		1.2	(0.4)		(3.0)
Total other income (expense):	(2.1)	(2.6)	(2.5)	(0.4)	0.2		(0.5)		(0.7)		(0.8)		(7.6)	(1.8)		(7.8)
Income before income tax	(7.7)	3.3	3.6	0.8	18.0		13.3		5.6		83.2		0.0	120.1		36.2
Income tax provision (benefit)	(3.4)	(3.6)	1.0	1.6	3.5		4.3		(25.3)		4.5		(4.4)	(13.0)		19.0
Net income	(4.3)	6.9	2.6	(0.8)	14.5		9.0		30.9		78.7		4.4	133.1		17.2
Net loss attributable to non-controlling interest	(0.1)			(0.1)			(0.1)				(0.1)		(0.2)	(0.2)		(0.2)
Net income attributable to Myriad Genetics, Inc. stockholders	$ (4.2)	$ 6.9	$ 2.6	$ (0.7)	$ 14.5		$ 9.1		$ 30.9		$ 78.8		$ 4.6	$ 133.3		$ 17.4
Earnings per share:
Basic	$ (0.06)	$ 0.09	$ 0.04	$ (0.01)	$ 0.21		$ 0.13		$ 0.45		$ 1.15		$ 0.06	$ 1.92		$ 0.25
Diluted	$ (0.06)	$ 0.09	$ 0.03	$ (0.01)	$ 0.20		$ 0.13		$ 0.43		$ 1.12		$ 0.06	$ 1.85		$ 0.25
Weighted average shares outstanding:
Basic	73.4	73.3	74.2	73.0	70.1		69.8		69.3		68.6		73.5	69.4		68.3
Diluted	74.8	74.9	76.5	73.0	72.9		72.4		71.9		70.4		76.0	72.0		68.8
Molecular Diagnostic Testing [Member]
Total revenue	$ 196.9	$ 200.5	$ 203.0	$ 189.0	$ 180.6		$ 169.3		$ 173.1		$ 167.4		$ 789.4	$ 690.4	[2]	$ 679.4	[2]
Costs and expenses:
Total costs and expenses	41.6	40.3	44.0	42.3	38.0		36.8		37.7		36.2		168.2	148.7		145.2
Pharmaceutical and Clinical Services [Member]
Total revenue	18.5	16.1	13.8	13.3	13.3		13.8		14.8		11.4		61.7	53.3	[2]	49.3	[2]
Costs and expenses:
Total costs and expenses	$ 9.0	$ 8.3	$ 8.1	$ 7.4	$ 7.7		$ 7.3		$ 6.7		$ 6.8		$ 32.8	$ 28.5		$ 26.0

[1] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements of this report for additional information.

[2] Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606)