Derivative Financial Instruments (Tables)

6 Months Ended

Mar. 31, 2019

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 March 31, 2019 and September 30, 2018:

	March 31, 2019
	Contract Amount				Fair Value
	Foreign Currency		US$		US$
	(In thousands)
Sell foreign currency:
Euro (EUR)	EUR	8,400	$	9,443	$	—
Buy foreign currency:
British pound (GBP)	GBP	8,851	$	11,600	$	—
Singapore dollar (SGD)	SGD	5,689	$	4,200	$	—

	September 30, 2018
	Contract Amount				Fair Value
	Foreign Currency		US$		US$
	(In thousands)
Sell foreign currency:
Euro (EUR)	EUR	9,000	$	10,372	$	—
Buy foreign currency:
British pound (GBP)	GBP	8,598	$	11,200	$	—
Singapore dollar (SGD)	SGD	9,580	$	7,000	$	—

Losses on Derivative Financial Instruments

Gains 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 March 31,				Six Months Ended March 31,
	2019		2018		2019		2018
	(In thousands)
Gains on foreign currency forward contracts	$	720	$	425	$	316	$	619