CONSOLIDATED STATEMENTS OF SHAREHOLDERS' 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, 2008	$ 1,539,000	$ 1,297,835	$ (1,061,663)	$ 2,508	$ 1,300,320
Balance (in shares) at Mar. 31, 2008		218,790,000	34,451,000
Components of other comprehensive income:
Net income	245,587	0	0	0	245,587
Net unrealized gains on available-for-sale investments, net of $1,669 of tax in year ended 3/31/2009, $1,778 of tax in year ended 3/31/2010, $493 of tax in year ended 3/31/2011	1,804	0	0	1,804	0
Total comprehensive income	247,391
Issuances from equity incentive plans	22,767	22,767	0	0	0
Issuances from equity incentive plans (in shares)		1,917,000	0
Employee stock purchase plan	10,788	10,788	0	0	0
Employee stock purchase plan (in shares)		545,000	0
Purchase of treasury stock	(123,929)	0	(123,929)	0	0
Purchase of treasury stock (in shares)		0	4,032,000
Treasury stock used for new issuances	0	(90,222)	90,222	0	0
Treasury stock used for new issuances (in shares)		(2,462,000)	(2,462,000)
Tax benefit from equity incentive plans	7,584	7,584	0	0	0
Share-based compensation	33,367	33,367	0	0	0
Cash dividend	(246,657)	0	0	0	(246,657)
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 on available-for-sale investments, net of $1,669 of tax in year ended 3/31/2009, $1,778 of tax in year ended 3/31/2010, $493 of tax in year ended 3/31/2011	(1,280)	0	0	(1,280)	0
Total comprehensive income	215,725
Issuances from equity incentive plans	27,108	27,108	0	0	0
Issuances from equity incentive plans (in shares)		1,955,000	0
Employee stock purchase plan	9,370	9,370	0	0	0
Employee stock purchase plan (in shares)		605,000	0
Treasury stock used for new issuances	0	(82,012)	82,012	0	0
Treasury stock used for new issuances (in shares)		(2,560,000)	(2,560,000)
Tax benefit from equity incentive plans	3,709	3,709	0	0	0
Share-based compensation	36,713	36,713	0	0	0
Cash dividend	(249,556)	0	0	0	(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	185,329,144	218,790,000	33,461,000
Components of other comprehensive income:
Net income	418,950				418,950
Net unrealized gains on available-for-sale investments, net of $1,669 of tax in year ended 3/31/2009, $1,778 of tax in year ended 3/31/2010, $493 of tax in year ended 3/31/2011	325	0	0	325	0
Total comprehensive income	419,275
Issuances from equity incentive plans	57,396	57,396	0	0	0
Issuances from equity incentive plans (in shares)		3,591,000	0
Employee stock purchase plan	14,544	14,544	0	0	0
Employee stock purchase plan (in shares)		622,000	0
Treasury stock used for new issuances	0	(125,283)	125,283	0	0
Treasury stock used for new issuances (in shares)		(4,213,000)	(4,213,000)
Tax benefit from equity incentive plans	7,523	7,523	0	0	0
Share-based compensation	37,131	37,131	0	0	0
Cash dividend	(256,811)	0	0	0	(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