CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total	Common Stock and Additional Paid-in Capital	Common Stock Held in Treasury	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance at Mar. 31, 2011	$ 1,812,438	$ 1,268,318	$ (888,075)	$ 3,357	$ 1,428,838
Balance, treasury stock, (shares) at Mar. 31, 2011			29,248,000
Balance, common stock shares issued (in shares) at Mar. 31, 2011		218,790,000
Net income	336,705				336,705
Other comprehensive income (loss)	(256)			(256)
Issuances from equity incentive plans (shares)		3,000,000
Issuances from equity incentive plans (amount)	42,596	42,596
Employee stock purchase plans (shares)		609,000
Employee stock purchase plans (amount)	14,861	14,861
Treasury stock used for new issuances (shares)		(3,609,000)	(3,609,000)
Treasury stock used for new issuances (amount)		(107,182)	107,182
Tax benefit (shortfall) from equity incentive plans	10,980	10,980
Share-based compensation	39,527	39,527
Cash dividend	(266,178)				(266,178)
Balance at Mar. 31, 2012	1,990,673	1,269,100	(780,893)	3,101	1,499,365
Balance, common stock shares issued (in shares) at Mar. 31, 2012		218,790,000
Balance, treasury stock, (shares) at Mar. 31, 2012			25,639,000
Net income	127,389				127,389
Other comprehensive income (loss)	3,834			3,834
Issuances from equity incentive plans (shares)		2,773,000
Issuances from equity incentive plans (amount)	19,935	19,935
Employee stock purchase plans (shares)		549,000
Employee stock purchase plans (amount)	15,760	15,760
Treasury stock used for new issuances (shares)		(3,322,000)	(3,322,000)
Treasury stock used for new issuances (amount)		(98,673)	98,673
Tax benefit (shortfall) from equity incentive plans	(9,896)	(9,896)
Share-based compensation	52,667	52,667
Non-cash consideration - SMSC acquisition	6,930	6,930
Cash dividend	(273,822)				(273,822)
Balance at Mar. 31, 2013	1,933,470	1,255,823	(682,220)	6,935	1,352,932
Balance, common stock shares issued (in shares) at Mar. 31, 2013	218,789,994	218,790,000
Balance, treasury stock, (shares) at Mar. 31, 2013	196,472,856		22,317,000
Net income	395,281				395,281
Other comprehensive income (loss)	(5,884)			(5,884)
Issuances from equity incentive plans (shares)		2,858,000
Issuances from equity incentive plans (amount)	17,658	17,658
Employee stock purchase plans (shares)		672,000
Employee stock purchase plans (amount)	19,788	19,788
Treasury stock used for new issuances (shares)		(3,530,000)	(3,530,000)
Treasury stock used for new issuances (amount)		(104,838)	104,838
Tax benefit (shortfall) from equity incentive plans	1,411	1,411
Share-based compensation	54,941	54,941
Cash dividend	(281,204)				(281,204)
Balance at Mar. 31, 2014	$ 2,135,461	$ 1,244,783	$ (577,382)	$ 1,051	$ 1,467,009
Balance, common stock shares issued (in shares) at Mar. 31, 2014	218,789,994	218,790,000
Balance, treasury stock, (shares) at Mar. 31, 2014	200,002,736		18,787,000