INCOME TAXES - Tax valuation allowance (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2016 USD ($) item	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Tax valuation allowance
Change in valuation allowance	$ 6,900	$ 35,800
Deferred tax asset valuation allowance	47,887	54,759
Net tax benefit before offset by amounts recorded through OCI	9,200
Accumulated earnings	813,035	818,642
Income tax accounting corrections
Income tax expense (benefit)	$ (9,212)	48,997	$ 19,831
Income Tax Accounting Errors
Income tax accounting corrections
Number of income tax accouting errors identified | item	2
Income Tax Accounting Errors | Previously Reported
Income tax accounting corrections
Income tax expense (benefit)		(3,000)
Income Tax Accounting Errors | Adjustments
Income tax accounting corrections
Income tax expense (benefit)	$ 3,000
Australia
Tax valuation allowance
Change in valuation allowance	(3,100)
Foreign
Tax valuation allowance
Foreign subsidiaries earnings on which income tax not provided	389,500
United Kingdom
Tax valuation allowance
Foreign subsidiaries earnings on which income tax not provided	360,000
U.S.
Tax valuation allowance
Change in valuation allowance	(3,800)	35,800
Deferred tax asset valuation allowance	43,700	$ 47,500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities, Current	23,800
Annual valuation allowance activity	$ 20,000