Earnings Per Share (Reconciliation of Net Earnings to Net Earnings Per Share Basic and Diluted) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share
Net earnings	$ 43,855us-gaap_NetIncomeLoss	$ 44,798us-gaap_NetIncomeLoss	$ 87,639us-gaap_NetIncomeLoss	$ 68,181us-gaap_NetIncomeLoss
Basic shares outstanding	65,159	66,633	65,242	67,182
Dilutive effect of stock options and restricted stock	1,381	1,272	1,399	1,281
Diluted shares outstanding	66,540	67,905	66,641	68,463
Basic earnings per share	$ 0.67us-gaap_EarningsPerShareBasic	$ 0.67us-gaap_EarningsPerShareBasic	$ 1.34us-gaap_EarningsPerShareBasic	$ 1.01us-gaap_EarningsPerShareBasic
Diluted earnings per share	$ 0.66us-gaap_EarningsPerShareDiluted	$ 0.66us-gaap_EarningsPerShareDiluted	$ 1.32us-gaap_EarningsPerShareDiluted	$ 1.00us-gaap_EarningsPerShareDiluted

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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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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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