Significant Accounting Policies (Details) (USD $)	3 Months Ended								12 Months Ended
	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2009	Jun. 30, 2009	Mar. 31, 2011	Mar. 31, 2010	Mar. 31, 2009
Notes to Financial Statements [Abstract]
Percentage of outstanding stock of all subsidiaries owned (in hundredths)	100.00%								100.00%
Amount of deferred revenue (gross)	$ 208,100,000				$ 148,400,000				$ 208,100,000	$ 148,400,000
Amount of deferred cost of sales	68,100,000				49,500,000				68,100,000	49,500,000
Amount of deferred Income on shipments to distributors	140,044,000				98,941,000				140,044,000	98,941,000
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)	29.04								29.04
Number of distributor with more than 10 percent of entity's net sales (in number of distributors)									1
Percentage of net sales from one distributor (in hundredths)	10.00%								10.00%
End customer's percentage of net sales or accounts receivable balances (in hundredths)									10.00%	10.00%	10.00%
Amount of distributor advances, included in deferred income on shipments to distributors in consolidated balance sheets	71,900,000				57,500,000				71,900,000	57,500,000
Number of days requiring distributor to settle receivable balances (in days)									30
Interest rate of junior subordinated convertible debentures (in hundredths)	2.125%								2.125%
Retrospective effect to condensed consolidated statements of income [Abstract]
Amount before application, interest expense											24,269,000
Amount before application, income before income taxes											237,250,000
Amount before application, income tax (benefit) provision											(11,570,000)
Amount before application, net Income											248,820,000
Amount before application, basic net income per common share											$ 1.36
Amount before application, diluted net income per common share											$ 1.33
Amount after application, interest expense									31,521,000	31,150,000	29,440,000
Amount after application, income before income taxes											232,079,000
Amount after application, income tax (benefit) provision									31,531,000	20,808,000	(13,508,000)
Amount after application, net Income									$ 418,950,000	$ 217,005,000	$ 245,587,000
Amount after application, basic net income per common share									$ 2.24	$ 1.18	$ 1.34
Amount after application, diluted net income per common share	$ 0.62	$ 0.51	$ 0.54	$ 0.47	$ 0.40	$ 0.37	$ 0.24	$ 0.15	$ 2.15	$ 1.16	$ 1.31