Fair Value Measurements - Schedule of Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) | Sep. 29, 2013 | Mar. 31, 2013 |
In Thousands, unless otherwise specified |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | $346,501 | $359,974 |
Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and cash equivalents | 86,507 | 95,532 |
Marketable securities | 346,501 | 359,974 |
Total assets at fair value disclosure | 433,008 | 455,506 |
U.S. government and agency securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 83,359 | 113,359 |
Corporate debt obligations [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 167,055 | 154,859 |
Mortgage-backed securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 52,387 | 51,281 |
Municipal bonds [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 41,007 | 39,872 |
Other debt securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 2,693 | 603 |
Fair Value Measurements Using, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and cash equivalents | 86,507 | 95,098 |
Marketable securities | 83,359 | 113,359 |
Total assets at fair value disclosure | 169,866 | 208,457 |
Fair Value Measurements Using, Level 1 [Member] | U.S. government and agency securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 83,359 | 113,359 |
Fair Value Measurements Using, Level 1 [Member] | Corporate debt obligations [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |
Fair Value Measurements Using, Level 1 [Member] | Mortgage-backed securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |
Fair Value Measurements Using, Level 1 [Member] | Municipal bonds [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |
Fair Value Measurements Using, Level 1 [Member] | Other debt securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |
Fair Value Measurements Using, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and cash equivalents | ' | 434 |
Marketable securities | 263,142 | 246,615 |
Total assets at fair value disclosure | 263,142 | 247,049 |
Fair Value Measurements Using, Level 2 [Member] | U.S. government and agency securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |
Fair Value Measurements Using, Level 2 [Member] | Corporate debt obligations [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 167,055 | 154,859 |
Fair Value Measurements Using, Level 2 [Member] | Mortgage-backed securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 52,387 | 51,281 |
Fair Value Measurements Using, Level 2 [Member] | Municipal bonds [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 41,007 | 39,872 |
Fair Value Measurements Using, Level 2 [Member] | Other debt securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | 2,693 | 603 |
Fair Value Measurements Using, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Cash and cash equivalents | ' | ' |
Marketable securities | ' | ' |
Total assets at fair value disclosure | ' | ' |
Fair Value Measurements Using, Level 3 [Member] | U.S. government and agency securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |
Fair Value Measurements Using, Level 3 [Member] | Corporate debt obligations [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |
Fair Value Measurements Using, Level 3 [Member] | Mortgage-backed securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |
Fair Value Measurements Using, Level 3 [Member] | Municipal bonds [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |
Fair Value Measurements Using, Level 3 [Member] | Other debt securities [Member] | Fair Value, Measurements, Recurring [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Marketable securities | ' | ' |