Inventories (Details) (USD $)	Sep. 30, 2012	Mar. 31, 2012
Business Acquisition [Line Items]
Raw materials	$ 7,934,000	$ 8,065,000
Work in process	187,734,000	139,045,000
Finished goods	93,858,000	70,168,000
Inventory, Net	289,526,000	217,278,000
SMSC Acquisition [Member]
Business Acquisition [Line Items]
Inventory valuation adjustment resulting from acquisition	$ 26,200,000