Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment reporting information [Line Items]
Net sales	$ 383,298	$ 340,602	$ 735,432	$ 715,109
Gross Profit	194,195	196,703	398,992	418,160
Semiconductor products [Member]
Segment reporting information [Line Items]
Net sales	363,177	318,618	695,029	672,478
Gross Profit	174,074	175,214	358,589	376,024
Technology licensing [Member]
Segment reporting information [Line Items]
Net sales	20,121	21,984	40,403	42,631
Gross Profit	$ 20,121	$ 21,489	$ 40,403	$ 42,136