CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock and Additional Paid-in Capital	Common Stock Held in Treasury	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Balance at Mar. 31, 2009	$ 1,490,311	$ 1,282,119	$ (1,095,370)	$ 4,312	$ 1,299,250
Balance (in shares) at Mar. 31, 2009		218,790,000	(36,021,000)
Components of other comprehensive income:
Net Income	217,005				217,005
Net unrealized gains (losses) on available-for-sale securities, net of tax	(1,280)			(1,280)
Total comprehensive income	215,725
Issuances from equity incentive plans (in shares)		1,955,000
Issuances from equity incentive plans (amount)	27,108	27,108
Employee stock purchase plans (shares)		605,000
Employee stock purchase plans (amount)	9,370	9,370
Treasury stock used for new issuances (shares)		(2,560,000)	2,560,000
Treasury stock used for new issuances (amount)		(82,012)	82,012
Tax benefit from equity incentive plans	3,709	3,709
Share-based compensation	36,713	36,713
Cash dividend	(249,556)				(249,556)
Balance at Mar. 31, 2010	1,533,380	1,277,007	(1,013,358)	3,032	1,266,699
Balance (in shares) at Mar. 31, 2010		218,790,000	(33,461,000)
Components of other comprehensive income:
Net Income	418,950				418,950
Net unrealized gains (losses) on available-for-sale securities, net of tax	325			325
Total comprehensive income	419,275
Issuances from equity incentive plans (in shares)		3,591,000
Issuances from equity incentive plans (amount)	57,396	57,396
Employee stock purchase plans (shares)		622,000
Employee stock purchase plans (amount)	14,544	14,544
Treasury stock used for new issuances (shares)		(4,213,000)	4,213,000
Treasury stock used for new issuances (amount)		(125,283)	125,283
Tax benefit from equity incentive plans	7,523	7,523
Share-based compensation	37,131	37,131
Cash dividend	(256,811)				(256,811)
Balance at Mar. 31, 2011	1,812,438	1,268,318	(888,075)	3,357	1,428,838
Balance (in shares) at Mar. 31, 2011	189,541,707	218,790,000	(29,248,000)
Components of other comprehensive income:
Net Income	336,705				336,705
Net unrealized gains (losses) on available-for-sale securities, net of tax	(256)			(256)
Total comprehensive income	336,449
Issuances from equity incentive plans (in 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 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 (in shares) at Mar. 31, 2012	193,150,532	218,790,000	(25,639,000)