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
	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net income attributable to Alpha and Omega Semiconductor Limited	$ 9,574	$ 1,009
Basic:
Weighted average number of common shares used to compute basic net income per share	25,340	24,538
Effect of potentially dilutive securities:
Stock options, RSUs and ESPP shares	974	592
Weighted average number of common shares used to compute diluted net income per share	26,314	25,130
Net income per share attributable to Alpha and Omega Semiconductor Limited:
Basic (in dollars per share)	$ 0.38	$ 0.04
Diluted (in dollars per share)	$ 0.36	$ 0.04