BUSINESS SEGMENTS AND GEOGRAPHIC INFORMATION - Reconciliation of Segment Operating Income (Loss) to Income from Continuing Operations Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain on sale of assets	$ 4,279	$ 5,545
Selling, general and administrative	49,808	54,508
Operating income from continuing operations	31,368	54,289
Other income (expense)
Interest and dividend income	2,214	2,450
Interest expense	(6,100)	(4,720)
Gain (loss) on investment securities	2,821	(42,844)
Gain on sale of subsidiary	14,963	0
Other	(399)	541
Total other income (expense)	13,499	(44,573)
Income from continuing operations before income taxes	44,867	9,716
Operating Segment
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Operating income from continuing operations	60,345	84,719
Segment Reconciling Items
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Gain on sale of assets	4,279	5,545
Corporate
Segment Reporting Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Abstract]
Selling, general and administrative	$ (33,256)	$ (35,975)

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Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Amount of the cost of borrowed funds accounted for as interest expense.

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Amount before accretion (amortization) of purchase discount (premium) of interest income and dividend income on nonoperating securities.

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The net result for the period of deducting operating expenses from operating revenues.

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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