Commitments and Contingencies - Purchase Commitments (Details) - USD ($) $ in Millions	6 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Jun. 30, 2015
Raw materials, wafers, and packaging and testing services puchase commitments
Purchase Commitment, Excluding Long-term Committment [Line Items]
Purchase commitment, amount		$ 39.4	$ 29.2
Property and equipment purchase commitments
Purchase Commitment, Excluding Long-term Committment [Line Items]
Purchase commitment, amount		$ 8.9	$ 3.7
Facility in Liangjiang New Area of Chongqing (the 'Joint Venture') [Member] | Scenario, Forecast [Member]
Purchase Commitment, Excluding Long-term Committment [Line Items]
Cash to be contributed to the Joint Venture prior to October 2016	$ 10.0