Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Segment Information - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015 Segment	Feb. 28, 2014	Aug. 31, 2014	Jul. 18, 2014
Segment Reporting Information [Line Items]
Number of reportable segments			3us-gaap_NumberOfReportableSegments
Total revenue	$ 630,149us-gaap_Revenues	$ 502,216us-gaap_Revenues	$ 1,125,207us-gaap_Revenues	$ 992,571us-gaap_Revenues
Total assets	1,690,409us-gaap_Assets		1,690,409us-gaap_Assets		1,517,168us-gaap_Assets
Earnings (loss) from unconsolidated affiliates	(185)	(67)	570	(26)
Investment in unconsolidated affiliates	71,225us-gaap_EquityMethodInvestments		71,225us-gaap_EquityMethodInvestments		69,359us-gaap_EquityMethodInvestments
GBW Railcar Services Holdings, LLC
Segment Reporting Information [Line Items]
Equity method investment, percentage of ownership interest						50.00%
Total revenue	83,300		165,900
Total assets	217,400		217,400		210,600
Earnings (loss) from unconsolidated affiliates	300		100
Investment in unconsolidated affiliates	$ 57,700		$ 57,700
GBW Railcar Services Holdings, LLC \| Watco Companies LLC
Segment Reporting Information [Line Items]
Equity method investment, percentage of ownership interest						50.00%