Short-term and Long-term Debt - CTBC Bank (Details)	1 Months Ended
	Jun. 30, 2020 USD ($)	May 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	May 31, 2020 TWD ($)	Jun. 30, 2019 TWD ($)
Short-term Debt [Line Items]
Short-term debt	$ 23,704,000			$ 24,047,000
Long-term debt, net of debt issuance costs	5,697,000			11,980,000
Secured debt | Term loan | CTBC Bank term loan, due August 31, 2021
Short-term Debt [Line Items]
Short-term debt	23,704,000			24,047,000
Secured debt | CTBC Bank | Term loan | CTBC Bank term loan, due August 31, 2021
Short-term Debt [Line Items]
Credit facility, term			12 months
Credit facility, maximum borrowing capacity			$ 24,000,000.0			$ 700,000,000.0
Long-term debt, net of debt issuance costs	$ 0			$ 0
Secured debt | CTBC Bank | Term loan | CTBC Bank term loan, due June 4, 2030
Short-term Debt [Line Items]
Credit facility, term		10 years
Credit facility, maximum borrowing capacity		$ 40,700,000			$ 1,200,000,000
Interest rate (as a percent)				0.45%
Collateral amount				$ 17,100,000
Percent of balances owed on commercial invoices, limitation on proceeds amount		80.00%			80.00%
Customs Bond | CTBC Bank | Term loan | CTBC Credit Facility, 12 Month, Up To 0.50% Interest
Short-term Debt [Line Items]
Credit facility, term			12 months
Credit facility, maximum borrowing capacity			$ 3,400,000			$ 100,000,000.0
Interest rate, stated percentage			0.50%			0.50%
Customs Bond | CTBC Bank | Term loan | CTBC Credit Facility, 180Day, Up To 100% Of Eligible Accounts Receivable, Between 0.30% And 0.50% Interest
Short-term Debt [Line Items]
Credit facility, term			180 days
Credit facility, maximum borrowing capacity			$ 51,500,000			$ 1,500,000,000.0
Percent of eligible accounts receivable			100.00%			100.00%
Customs Bond | CTBC Bank | Line of Credit | CTBC Bank term loan, due August 31, 2021
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity			$ 50,000,000.0
Customs Bond | CTBC Bank | Line of Credit | CTBC Credit Facility, 12 Month, Up To 100% Of Eligible Accounts Receivable, Between 0.30% And 0.50% Interest
Short-term Debt [Line Items]
Credit facility, term			12 months
Credit facility, maximum borrowing capacity			$ 50,000,000.0
Percent of eligible accounts receivable			100.00%			100.00%
Revolving Credit Facility | Line of Credit | CTBC Bank term loan, due August 31, 2021
Short-term Debt [Line Items]
Credit facility, remaining borrowing capacity				26,000,000.0
Collateral amount				$ 25,300,000
CTBC's Established NTD Interest Rate | Secured debt | CTBC Bank | Term loan | CTBC Bank term loan, due August 31, 2021
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)			0.25%
Two-Year Term Floating Rate Of Postal Saving Interest Rate [Member] | Secured debt | CTBC Bank | Term loan | CTBC Bank term loan, due June 4, 2030
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)	0.105%
Base Rate [Member] | Secured debt | CTBC Bank | Term loan | CTBC Bank term loan, due June 4, 2030
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)	4.00%
Minimum | Customs Bond | CTBC Bank | Line of Credit | CTBC Credit Facility, 12 Month, Up To 100% Of Eligible Accounts Receivable, Between 0.30% And 0.50% Interest
Short-term Debt [Line Items]
Increase to stated rate			0.80%
Minimum | CTBC's Established NTD Interest Rate | Customs Bond | CTBC Bank | Term loan | CTBC Credit Facility, 180Day, Up To 100% Of Eligible Accounts Receivable, Between 0.30% And 0.50% Interest
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)			0.30%
Minimum | CTBC's Established USD Interest Rate | Customs Bond | CTBC Bank | Line of Credit | CTBC Credit Facility, 12 Month, Up To 100% Of Eligible Accounts Receivable, Between 0.30% And 0.50% Interest
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)			0.30%
Maximum | CTBC Bank
Short-term Debt [Line Items]
Interest rate (as a percent)	0.63%			0.73%
Maximum | CTBC's Established NTD Interest Rate | Customs Bond | CTBC Bank | Term loan | CTBC Credit Facility, 180Day, Up To 100% Of Eligible Accounts Receivable, Between 0.30% And 0.50% Interest
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)			0.50%
Maximum | CTBC's Established USD Interest Rate | Customs Bond | CTBC Bank | Line of Credit | CTBC Credit Facility, 12 Month, Up To 100% Of Eligible Accounts Receivable, Between 0.30% And 0.50% Interest
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)			0.50%
Term loan | Secured debt | CTBC Bank term loan, due June 4, 2030
Short-term Debt [Line Items]
Long-term debt, net of debt issuance costs	$ 5,697,000			$ 11,980,000