Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Sep. 29, 2012	Mar. 31, 2012
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	$ 3,135,139	$ 3,063,038
Derivative financial instruments, net	2,402	3,070
Fair Value Liabilities, Convertible debentures - embedded derivative	1,545	931
Total liabilities measured at fair value	1,545	4,001
Net assets measured at fair value	3,133,594	3,059,037
Fair Value, Inputs, Level 1 [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	669,300	647,355
Derivative financial instruments, net	0	0
Fair Value Liabilities, Convertible debentures - embedded derivative	0	0
Total liabilities measured at fair value	0	0
Net assets measured at fair value	669,300	647,355
Fair Value, Inputs, Level 2 [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	2,436,770	2,386,754
Derivative financial instruments, net	2,402	3,070
Fair Value Liabilities, Convertible debentures - embedded derivative	0	0
Total liabilities measured at fair value	0	3,070
Net assets measured at fair value	2,436,770	2,383,684
Fair Value, Inputs, Level 3 [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	29,069	28,929
Derivative financial instruments, net	0	0
Fair Value Liabilities, Convertible debentures - embedded derivative	1,545	931
Total liabilities measured at fair value	1,545	931
Net assets measured at fair value	27,524	27,998
Cash And Cash Equivalents [Member] | Money Market Funds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	165,775	232,017
Cash And Cash Equivalents [Member] | Bank Certificates of Deposit [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	29,997	29,994
Cash And Cash Equivalents [Member] | Commercial Paper [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	158,233	233,980
Cash And Cash Equivalents [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	120,007	160,021
Cash And Cash Equivalents [Member] | Foreign Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	49,993	68,993
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	165,775	232,017
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Bank Certificates of Deposit [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	110,009	75,036
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Bank Certificates of Deposit [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	29,997	29,994
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	158,233	233,980
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	9,998	84,985
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	49,993	68,993
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Bank Certificates of Deposit [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Bank Certificates of Deposit [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	134,930	129,978
Short-Term Investments [Member] | Commercial Paper [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	328,905	360,887
Short-Term Investments [Member] | Corporate Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	25,768	14,257
Short-Term Investments [Member] | Municipal Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	3,473
Short-Term Investments [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	408,301	442,694
Short-Term Investments [Member] | Foreign Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	209,942	180,958
Short-Term Investments [Member] | Mortgage-Backed Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	19	31
Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Bank Certificates of Deposit [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	356,044	322,763
Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-Backed Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Bank Certificates of Deposit [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	134,930	129,978
Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	328,905	360,887
Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	25,768	14,257
Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	3,473
Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	52,257	119,931
Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	209,942	180,958
Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-Backed Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	19	31
Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Bank Certificates of Deposit [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-Backed Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Corporate Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	223,462	175,415
Long-Term Investments [Member] | Auction Rate Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	29,069	28,929
Long-Term Investments [Member] | Municipal Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	14,232	26,160
Long-Term Investments [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	101,408	66,198
Long-Term Investments [Member] | Mortgage-Backed Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	1,087,735	892,745
Long-Term Investments [Member] | Debt Mutual Fund [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	41,488	19,781
Long-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Auction Rate Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	37,472	17,539
Long-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-Backed Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Debt Mutual Fund [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	223,462	175,415
Long-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Auction Rate Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	14,232	26,160
Long-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	63,936	48,659
Long-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-Backed Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	1,087,735	892,745
Long-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Mutual Fund [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	41,488	19,781
Long-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Auction Rate Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	29,069	28,929
Long-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal Bonds [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Government and Agency Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-Backed Securities [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	0	0
Long-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Debt Mutual Fund [Member]
Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total assets measured at fair value	$ 0	$ 0