DERIVATIVE FINANCIAL INSTRUMENTS, Cash Flow Hedges, Foreign Currency Contracts and Net Investment Contracts (Details) ₩ in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 KRW (₩)
Foreign Exchange Contracts [Member] | Buy [Member]
Derivative Instruments [Abstract]
Derivative notional amount		$ 2,981	$ 7,652
Foreign Exchange Contracts [Member] | Sell [Member]
Derivative Instruments [Abstract]
Derivative notional amount		$ 30,235	$ 24,860
Net Investment Hedging [Member]
Derivative Instruments [Abstract]
Derivative notional amount | ₩				₩ 100,000,000
Amount recogized in Other comprehensive income	$ 3,241