Reconciliation of Numerators and Denominators of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Numerator for diluted and basic earnings per share:
Net income	$ 14,407us-gaap_NetIncomeLoss	$ 16,977us-gaap_NetIncomeLoss
Denominator - share:
Basic weighted-average shares	31,936	34,699
Effect of dilutive securities	1,192	1,121
Diluted weighted-average shares	33,128	35,820
Earnings per share:
Basic (in dollars per share)	$ 0.45us-gaap_EarningsPerShareBasic	$ 0.49us-gaap_EarningsPerShareBasic
Diluted (in dollars per share)	$ 0.43us-gaap_EarningsPerShareDiluted	$ 0.47us-gaap_EarningsPerShareDiluted

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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