Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Accounting Policies [Abstract]
Percentage Of Outstanding Stock Of All Subsidiaries Owned	100.00%
Amount of deferred revenue (gross)	$ 159,100,000	$ 208,100,000
Amount of deferred cost of sales	50,400,000	68,100,000
Amount of deferred Income on shipments to distributors	108,709,000	140,044,000
Estimated useful lives, lower range (in years)	3
Estimated useful lives, upper range (in years)	30
Junior subordinated convertible debentures conversion price per share (in dollars per share)	$ 27.94
Amount of distributor advances, included in deferred income on shipments to distributors in consolidated balance sheets	$ 51,700,000	$ 71,900,000
Number of days requiring distributor to settle receivable balances (in days)	30