Quantum Corporation Annual report pursuant to Section 13 and 15(d)

NET INCOME (LOSS) PER SHARE - Narrative (Details)

NET INCOME (LOSS) PER SHARE - Narrative (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Jun. 23, 2009	Nov. 15, 2010	Oct. 31, 2012
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from anti-dilutive shares excluded from computations (in shares)	2.4	12.8	17.3
Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from anti-dilutive shares excluded from computations (in shares)	0.1	11.0	10.1
EMC Corporation
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of shares called by warrants (in shares)				10
Exercise price (usd per share)				$ 0.38
3.50% Convertible Subordinated Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate (as a percent)	3.50%
Conversion price (usd per share)	4.33				$ 4.33
Anti-dilutive shares excluded from anti-dilutive shares excluded from computations (in shares)	29.0	31.1	31.2
Anti-dilutive income excluded from computations	5.3	5.7	5.7
4.50% Convertible Subordinated Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate (as a percent)	4.50%
Conversion price (usd per share)	1.65					$ 1.65
Anti-dilutive shares excluded from anti-dilutive shares excluded from computations (in shares)	42.5	42.5	17.6
Anti-dilutive income excluded from computations	3.6	3.6	1.5