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Net Income (Loss) Per Share - Schedule of Calculation of Basic and Diluted Net Income (Loss) Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	May 03, 2015	Jan. 25, 2015	Oct. 26, 2014	Jul. 27, 2014	Apr. 27, 2014	Jan. 26, 2014	Oct. 27, 2013	Jul. 28, 2013	May 03, 2015	Apr. 27, 2014	Apr. 28, 2013	Dec. 31, 2013
Numerator:
Numerator for basic income (loss) per share	$ 7,327us-gaap_NetIncomeLoss	$ 1,678us-gaap_NetIncomeLoss	$ (11,361)us-gaap_NetIncomeLoss	$ 14,243us-gaap_NetIncomeLoss	$ 28,750us-gaap_NetIncomeLoss	$ 27,061us-gaap_NetIncomeLoss	$ 29,965us-gaap_NetIncomeLoss	$ 26,011us-gaap_NetIncomeLoss	$ 11,887us-gaap_NetIncomeLoss	$ 111,787us-gaap_NetIncomeLoss	$ (5,454)us-gaap_NetIncomeLoss
Interest expense on 5.0% Convertible Senior Notes due 2029									0	2,157	0
Numerator for diluted income (loss) per share									$ 11,887	$ 113,944	$ (5,454)
Denominator:
Denominator for basic income (loss) per share - weighted average shares	104,005	103,563	99,621	98,241	96,965	96,394	95,941	94,609	101,408	95,979	92,860
Effect of dilutive securities:
Stock options and restricted stock units									3,562	4,385	0
5.0% Convertible Senior Notes due 2029									0	3,748	0
Dilutive potential common shares									3,562	8,133	0
Denominator for diluted income (loss) per share	107,535	105,990	99,621	106,036	105,418	104,361	103,696	101,125	104,970	104,112	92,860
Net income (loss) per share attributable to Finisar Corporation common stockholders:
Basic (in usd)	$ 0.07us-gaap_EarningsPerShareBasic	$ 0.02us-gaap_EarningsPerShareBasic	$ (0.11)us-gaap_EarningsPerShareBasic	$ 0.14us-gaap_EarningsPerShareBasic	$ 0.30us-gaap_EarningsPerShareBasic	$ 0.28us-gaap_EarningsPerShareBasic	$ 0.31us-gaap_EarningsPerShareBasic	$ 0.27us-gaap_EarningsPerShareBasic	$ 0.12us-gaap_EarningsPerShareBasic	$ 1.16us-gaap_EarningsPerShareBasic	$ (0.06)us-gaap_EarningsPerShareBasic
Diluted (in usd)	$ 0.07us-gaap_EarningsPerShareDiluted	$ 0.02us-gaap_EarningsPerShareDiluted	$ (0.11)us-gaap_EarningsPerShareDiluted	$ 0.14us-gaap_EarningsPerShareDiluted	$ 0.28us-gaap_EarningsPerShareDiluted	$ 0.26us-gaap_EarningsPerShareDiluted	$ 0.29us-gaap_EarningsPerShareDiluted	$ 0.26us-gaap_EarningsPerShareDiluted	$ 0.11us-gaap_EarningsPerShareDiluted	$ 1.09us-gaap_EarningsPerShareDiluted	$ (0.06)us-gaap_EarningsPerShareDiluted
5.0% Convertible Senior Notes Due 2029
Debt Instrument [Line Items]
Interest rate	5.00%				5.00%				5.00%	5.00%
0.5% Convertible Senior Notes Due 2033
Debt Instrument [Line Items]
Interest rate	0.50%				0.50%				0.50%	0.50%		0.50%