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Fair Value Measurements (Details) - USD ($)
$ in Thousands
Jun. 27, 2015
Mar. 28, 2015
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Available-for-sale Securities, Noncurrent $ 248,431 $ 266,902 [1]
Fair Value, Inputs, Level 3 [Member] | Auction Rate Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Available-for-sale Securities, Noncurrent 10,409  
Fair Value, Measurements, Recurring [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 3,468,910 3,471,356
Liabilities measured at fair value 4,084 9,251
Net assets measured at fair value 3,464,826 3,462,105
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 544,378 492,097
Liabilities measured at fair value 0 0
Net assets measured at fair value 544,378 492,097
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 2,914,123 2,968,947
Liabilities measured at fair value 4,084 9,251
Net assets measured at fair value 2,910,039 2,959,696
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 10,409 10,312
Liabilities measured at fair value 0 0
Net assets measured at fair value 10,409 10,312
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Money Market Funds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 304,935 235,583
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 65,000 229,999
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Non-financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 84,987 89,995
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | U.S. Government and Agency Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 33,999 200,392
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 475  
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Foreign Government and Agency Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 64,996 37,996
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 304,935 235,583
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Non-financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0  
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 65,000 229,999
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Non-financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 84,987 89,995
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 33,999 200,392
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 475  
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 64,996 37,996
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Non-financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Cash And Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0  
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 225,000 75,000
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Non-financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 340,390 339,029
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | U.S. Government and Agency Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 541,964 557,524
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 46,056 40,006
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Foreign Government and Agency Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 136,049 159,936
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Mortgage-Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 921,391 897,776
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Debt Mutual Fund [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 38,569 38,608
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Bank Loans [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 99,835 98,100
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Asset-backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 212,691 204,510
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Commercial Mortgage Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 104,142  
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Non-financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 239,443 256,514
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Debt Mutual Fund [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Bank Loans [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Asset-backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Mortgage Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0  
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 225,000 75,000
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Non-financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 340,390 339,029
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 302,521 301,010
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 46,056 40,006
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 136,049 159,936
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 921,391 897,776
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Debt Mutual Fund [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 38,569 38,608
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Bank Loans [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 99,835 98,100
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Asset-backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 212,691 204,510
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Mortgage Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 104,142  
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Non-financial institution securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Debt Mutual Fund [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Bank Loans [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Short-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Mortgage Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0  
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 7,522 9,650
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Mortgage-Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 166,558 182,400
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Debt Mutual Fund [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 55,779 56,592
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Asset-backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 7,618 7,948
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Commercial Mortgage Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 545  
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Auction Rate Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value   10,312
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Asset-backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Mortgage Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0  
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 7,522 9,650
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 166,558 182,400
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 55,779 56,592
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Asset-backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 7,618 7,948
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Mortgage Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 545  
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal Bonds [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Asset-backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0 0
Fair Value, Measurements, Recurring [Member] | Long-Term Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Mortgage Backed Securities [Member]    
Assets and Liabilities Measured at Fair Value on a Recurring Basis    
Assets measured at fair value 0  
Fair Value, Measurements, Recurring [Member] | 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    
Assets measured at fair value $ 10,409 $ 10,312
[1] Derived from audited financial statements