The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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- Definition

Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified		1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 07, 2010 Plan 2010	Sep. 15, 2011 Common Stock	Jan. 31, 2013 Common Stock	Jan. 31, 2012 Common Stock	Jan. 31, 2013 Common Stock	Jan. 31, 2012 Common Stock
Class of Stock [Line Items]
Stock repurchase program, authorized amount		$ 25
Share repurchase program, term		The Company will determine the timing and amount of the transactions based on its evaluation of market conditions and other factors. The repurchase program may be suspended or discontinued at any time and has no expiration date.
Stock repurchased during period, shares			124,229	226,710	1,642,272	1,121,600
Stock repurchased during period, value			0.7	1.2	9.2	6.1
Cumulative stock repurchased, shares			3,294,666		3,294,666
Cumulative stock repurchased, value			$ 18.7		$ 18.7
Share-based compensation common stock issuable shares authorized	4,800,000