Annual report pursuant to Section 13 and 15(d)

NET INCOME (LOSS) PER SHARE - Net Income (Loss) Per Share (Details)

v2.4.1.9
NET INCOME (LOSS) PER SHARE - Net Income (Loss) Per Share (Details) (USD $)
In Thousands, except Per Share data, unless otherwise specified
3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2013
Earnings Per Share [Abstract]                      
Net income (loss) $ 12,905us-gaap_NetIncomeLoss $ 6,931us-gaap_NetIncomeLoss $ 1,248us-gaap_NetIncomeLoss $ (4,324)us-gaap_NetIncomeLoss $ (14,404)us-gaap_NetIncomeLoss $ (2,458)us-gaap_NetIncomeLoss $ (7,893)us-gaap_NetIncomeLoss $ 3,281us-gaap_NetIncomeLoss $ 16,760us-gaap_NetIncomeLoss $ (21,474)us-gaap_NetIncomeLoss $ (52,179)us-gaap_NetIncomeLoss
Weighted average shares:                      
Basic                 254,665us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 247,024us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 239,855us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Dilutive shares from stock plans                 5,362qtm_DilutiveCommonShareEquivalentsFromStockPlans 0qtm_DilutiveCommonShareEquivalentsFromStockPlans 0qtm_DilutiveCommonShareEquivalentsFromStockPlans
Diluted                 260,027us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 247,024us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 239,855us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
Basic net income (loss) per share $ 0.05us-gaap_EarningsPerShareBasic $ 0.03us-gaap_EarningsPerShareBasic $ 0.00us-gaap_EarningsPerShareBasic $ (0.02)us-gaap_EarningsPerShareBasic         $ 0.07us-gaap_EarningsPerShareBasic $ (0.09)us-gaap_EarningsPerShareBasic $ (0.22)us-gaap_EarningsPerShareBasic
Diluted net income (loss) per share $ 0.04us-gaap_EarningsPerShareDiluted $ 0.03us-gaap_EarningsPerShareDiluted $ 0.00us-gaap_EarningsPerShareDiluted $ (0.02)us-gaap_EarningsPerShareDiluted         $ 0.06us-gaap_EarningsPerShareDiluted $ (0.09)us-gaap_EarningsPerShareDiluted $ (0.22)us-gaap_EarningsPerShareDiluted