Earnings Per Share - Schedule of Computation of Basic and Diluted Net (Loss) Income per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		12 Months Ended
		Sep. 26, 2015	Sep. 27, 2014	Jun. 27, 2015
Numerator:
Net (loss) income		$ (0.2)	$ 4.3	$ (3.4)
Less: Dividends on Series A Preferred Stock		(0.1)
Less: Accretion of Series A Preferred Stock		(9.7)
Net (loss) income attributable to common shareholders		$ (10.0)	$ 4.3
Denominator:
Weighted-average number of common shares outstanding - basic and diluted	[1]	58.8	58.8
Net (loss) income per share attributable to common stockholders	[1]	$ (0.17)	$ 0.07

[1] On August 1, 2015, JDS Uniphase Corporation (“JDSU”) distributed 47.1 million shares, or 80.1% of the outstanding shares of common stock of Lumentum Holdings Inc. (“we”, “our”, “Company” or “Lumentum”) to existing holders of JDSU common stock. JDSU was renamed Viavi Solutions Inc. (“Viavi”) and at the time of the distribution, retained 11.7 million shares, or 19.9% of Lumentum’s outstanding shares. Basic and diluted net (loss) income per share for the three months ended September 27, 2014 is calculated using the shares of Lumentum common stock outstanding on August 1, 2015, as if such shares were outstanding for the entire period.