Stock-based compensation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
Jul. 31, 2011
Summarized activity related to stock options
Number of Options Outstanding, Beginning Balance	2,362
Number of Options, Granted	287
Number of Options, Exercised	(784)
Number of Options, Forfeited or expired	(9)
Number of Options Outstanding, Ending Balance	1,856
Number of Options, Vested or expected to vest	1,778
Number of Options, Exercisable	947
Weighted Average Exercise Price Per Share, Outstanding, Beginning Balance	$ 20.15
Weighted Average Exercise Price Per Share, Granted	$ 43.32
Weighted Average Exercise Price Per Share, Exercised	$ 18.94
Weighted Average Exercise Price Per Share, Forfeited or expired	$ 26.47
Weighted Average Exercise Price Per Share, Outstanding, Ending Balance	$ 24.21
Weighted Average Exercise Price Per Share, Vested or expected to vest	$ 23.92
Weighted Average Exercise Price Per Share, Exercisable	$ 19.77
Aggregate Intrinsic Value, Outstanding	$ 49,786
Aggregate Intrinsic Value, Vested or expected to vest	48,191
Aggregate Intrinsic Value, Exercisable	$ 29,616
Weighted Average Remaining Term, Outstanding	6.4
Weighted Average Remaining Term, Vested or expected to vest	6.3
Weighted Average Remaining Term, Exercisable	4.8

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The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of vested portions of options outstanding and currently exercisable under the option plan as of the balance-sheet date.

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The number of shares into which fully or partially vested stock options outstanding as of the balance-sheet date can be currently converted under the option plan.

+ References

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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The weighted average period between the balance-sheet date and expiration for all vested portions of options outstanding and currently exercisable (or convertible) under the plan, which may be expressed in a decimal value for number of years.

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The decrease in the number of reserved shares that could potentially be issued attributable to the exercise or conversion during the reporting period of previously issued stock options under the option plan.

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The weighted average price at which option holders acquired shares when converting their stock options into shares under the plan during the reporting period.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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For presentations that combine terminations, the weighted average price of expired options and the price at which grantees could have acquired the underlying shares with respect to stock options that were terminated during the reporting period due to noncompliance with plan terms during the reporting period .

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The quantity of shares issuable on stock options awarded under the plan during the reporting period.

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The weighted average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on stock options awarded under the plan during the reporting period.

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The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices pertaining to options outstanding under the plan as of the balance-sheet date.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance-sheet date, including vested options.

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The weighted average price as of the beginning of the year at which grantees can acquire the shares reserved for issuance under the stock option plan.

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The weighted average period between the balance-sheet date and expiration for all awards outstanding under the plan, which may be expressed in a decimal value for number of years.

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As of the balance sheet date, the total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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The weighted-average period between the balance-sheet date and expiration date for fully vested and expected to vest options outstanding, which may be expressed in a decimal value for number of years.

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