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Financial Instruments Available for Sale Securities Gain/Loss Activity (Details) (USD $)
6 Months Ended
Jul. 31, 2014
Jul. 31, 2013
Financial Instruments [Abstract]    
Other than temporary impairment losses, investments $ 3,200,000 $ 0
Gain (loss) on investments 600,000 (200,000)
Proceeds from sale and maturity of marketable securities $ 534,400,000 $ 447,000,000