Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References+ Details

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

+ References+ Details

- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References+ Details

Stock-Based Benefit Plans (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
Stock-Based Benefit Plans (Details) (USD $)	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2012	Apr. 30, 2011	Oct. 31, 2012	Oct. 31, 2011
Weighted-average assumptions and the fair value used for stock option grants
Weighted-average volatility					46.99%	47.73%
Weighted-average grant date fair value per share of options granted					$ 8.70	$ 7.94
Stock-based compensation expense recognized and estimated amount to be recognized
Stock based expense recognized	$ 3,205,000	$ 2,345,000	$ 8,831,000	$ 7,717,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Payments					0	0
Employee Stock Option [Member]
Stock-based compensation expense recognized and estimated amount to be recognized
Stock based expense recognized	$ 1,225,000	$ 1,317,000	$ 4,745,000	$ 5,905,000
Maximum [Member]
Weighted-average assumptions and the fair value used for stock option grants
Expected volatility					50.24%	49.46%
Risk-free interest rate					1.77%	3.09%
Expected life (years)					9.06	8.75
Minimum [Member]
Weighted-average assumptions and the fair value used for stock option grants
Expected volatility					44.20%	45.38%
Risk-free interest rate					0.78%	1.64%
Expected life (years)					4.59	4.29