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Stock-based Compensation Plans and Awards (Details) (USD $)
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3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 3 Months Ended | 0 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | ||||
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Jul. 31, 2013
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Jul. 31, 2012
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Jul. 31, 2013
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Jul. 31, 2012
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Jul. 31, 2013
Stock Options
Black-Scholes option pricing model
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Jul. 31, 2013
Stock Options
Black-Scholes option pricing model
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Jul. 31, 2012
Stock Options
Black-Scholes option pricing model
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Apr. 30, 2013
Stock option with market and service conditions
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Jul. 06, 2013
Stock option with market and service conditions
Mr. Joseph Kennedy
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Mar. 22, 2012
Stock option with market and service conditions
Mr. Joseph Kennedy
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Jul. 31, 2013
Stock option with market and service conditions
Mr. Joseph Kennedy
Monte-Carlo simulation option pricing model
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Jul. 31, 2013
Restricted stock units
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Jul. 31, 2013
Restricted stock units
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| Assumptions used to calculate per-share fair value of stock option at the date of grant | |||||||||||||
| Expected life | 6 years 29 days | 6 years 3 months 14 days | 6 years 8 months 1 day | 10 years | |||||||||
| Risk-free interest rate (as a percent) | 1.08% | 1.18% | 1.52% | 2.33% | |||||||||
| Expected volatility (as a percent) | 59.00% | 58.00% | 57.00% | 70.00% | |||||||||
| Expected dividend yield (as a percent) | 0.00% | 0.00% | 0.00% | ||||||||||
| Stock price (in dollars per share) | $ 10.63 | ||||||||||||
| Stock-based compensation expense | $ 10,542,000 | $ 6,037,000 | $ 17,923,000 | $ 11,537,000 | $ 7,400,000 | $ 13,200,000 | |||||||
| Granted (in shares) | 800,000 | ||||||||||||
| Exercise price (in dollars per share) | $ 10.63 | ||||||||||||
| Period of time that the trailing weighted average stock price must exceed a certain price for the stock award to vest, prior to July 6, 2017 | 60 days | ||||||||||||
| Share price, under a sale of the entity, that must be obtained for the stock award to vest prior to July, 6, 2017 (in dollars per share) | $ 21.00 | ||||||||||||
| Share price that must be obtained for the stock award to vest prior to July, 6, 2017 (in dollars per share) | $ 21.00 | ||||||||||||
| Vesting term | 4 years | 4 years | |||||||||||
| Weighted-average fair value of stock option granted (in dollars per share) | $ 6.08 | ||||||||||||
| Lower stock-based compensation expense | $ 1,700,000 | ||||||||||||