Quarterly report pursuant to Section 13 or 15(d)

SUBSEQUENT EVENT (Details)

v2.4.1.9
SUBSEQUENT EVENT (Details) (3.50% convertible subordinated notes, USD $)
 3 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Apr. 24, 2014
Dec. 31, 2013
Jan. 28, 2015
Subsequent Event [Line Items]          
Interest per annum on the principal amount   3.50%us-gaap_DebtInstrumentInterestRateStatedPercentage 3.50%us-gaap_DebtInstrumentInterestRateStatedPercentage 3.50%us-gaap_DebtInstrumentInterestRateStatedPercentage  
Forecast
          
Subsequent Event [Line Items]          
Unamortized debt costs $ 300,000us-gaap_WriteOffOfDeferredDebtIssuanceCost
/ us-gaap_DebtInstrumentAxis
= qtm_ConvertibleSubordinatedThreeAndHalfPercentNotesMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember 		       
Accrued interest paid 400,000us-gaap_InterestPaid
/ us-gaap_DebtInstrumentAxis
= qtm_ConvertibleSubordinatedThreeAndHalfPercentNotesMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember 		       
Subsequent event
          
Subsequent Event [Line Items]          
Aggregate principal amount         50,000,000.0us-gaap_DebtInstrumentRepurchasedFaceAmount
/ us-gaap_DebtInstrumentAxis
= qtm_ConvertibleSubordinatedThreeAndHalfPercentNotesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
Interest per annum on the principal amount         3.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= qtm_ConvertibleSubordinatedThreeAndHalfPercentNotesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
Repurchase amount         51,000,000us-gaap_DebtInstrumentRepurchaseAmount
/ us-gaap_DebtInstrumentAxis
= qtm_ConvertibleSubordinatedThreeAndHalfPercentNotesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember
Loss on debt extinguishment 1,300,000us-gaap_GainsLossesOnExtinguishmentOfDebtBeforeWriteOffOfDeferredDebtIssuanceCost
/ us-gaap_DebtInstrumentAxis
= qtm_ConvertibleSubordinatedThreeAndHalfPercentNotesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember 		       
Loss from notes repurchased $ 1,000,000us-gaap_GainsLossesOnExtinguishmentOfDebt
/ us-gaap_DebtInstrumentAxis
= qtm_ConvertibleSubordinatedThreeAndHalfPercentNotesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember