Net Income Per Common Share Attributable to Alpha and Omega Semiconductor Limited - Basic and Diluted Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net loss attributable to Alpha and Omega Semiconductor Limited	$ (6,495)	$ (1,555)	$ (6,491)	$ (684)
Basic:
Weighted average number of common shares used to compute basic net loss per share	24,894	24,084	24,711	23,938
Effect of potentially dilutive securities:
Stock options, RSUs and ESPP shares	0	0	0	0
Weighted average number of common shares used to compute diluted net loss per share	24,894	24,084	24,711	23,938
Net loss per share attributable to Alpha and Omega Semiconductor Limited:
Basic (in dollars per share)	$ (0.26)	$ (0.06)	$ (0.26)	$ (0.03)
Diluted (in dollars per share)	$ (0.26)	$ (0.06)	$ (0.26)	$ (0.03)