Segment and Geographic Information - Revenue by Location and Product Type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 106,852	$ 109,067	$ 342,514	$ 339,064
Power discrete
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	89,932	89,936	291,964	275,485
Power IC
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	15,699	17,631	46,078	56,430
Packaging and testing services
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1,221	1,500	4,472	7,149
Hong Kong
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	90,050	87,143	280,396	265,914
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	13,607	18,834	46,690	63,991
South Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1,861	260	10,130	568
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	830	1,684	2,829	5,624
Other countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 504	$ 1,146	$ 2,469	$ 2,967