Derivative Financial Instruments (Tables)

3 Months Ended

Dec. 31, 2017

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Summary of Outstanding Foreign Currency Forward Contracts

The following tables summarize our outstanding foreign currency forward contracts, by currency, at December 31, 2017 and September 30, 2017:

	December 31, 2017
	Contract Amount				Fair Value
	Foreign Currency		US$		US$
	(In thousands)
Sell foreign currency:
Euro (EUR)	EUR	7,350	$	8,825	$	—
Buy foreign currency:
British pound (GBP)	GBP	5,398	$	7,300	$	—
Singapore dollar (SGD)	SGD	7,734	$	5,800	$	—

	September 30, 2017
	Contract Amount				Fair Value
	Foreign Currency		US$		US$
	(In thousands)
Sell foreign currency:
Euro (EUR)	EUR	5,050	$	5,968	$	—
Buy foreign currency:
British pound (GBP)	GBP	9,341	$	12,500	$	—

Losses on Derivative Financial Instruments

Gains (losses) on derivative financial instruments are recorded in our condensed consolidated statements of income and comprehensive income as a component of other income (expense), net, and consisted of the following: 

	Quarter Ended December 31,
	2017		2016
	(In thousands)
Gains (losses) on foreign currency forward contracts	$	194	$	(560	)