Fair Value of Assets and Liabilities - Securities (Details) (Fair Value, Measurements, Recurring [Member], USD $) | Mar. 30, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Estimate of Fair Value, Fair Value Disclosure [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Equity securities - mutual funds | $6,254 | $5,287 |
Derivative contracts, net | -2,936 | -1,113 |
Assets, fair value | 178,636 | 154,356 |
Estimate of Fair Value, Fair Value Disclosure [Member] | U.S. Government-backed securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 15,092 | 10,128 |
Estimate of Fair Value, Fair Value Disclosure [Member] | Agency bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 52,967 | 37,961 |
Estimate of Fair Value, Fair Value Disclosure [Member] | Commercial paper [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 34,989 | 39,987 |
Estimate of Fair Value, Fair Value Disclosure [Member] | Certificates of deposit [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 8,578 | 7,786 |
Estimate of Fair Value, Fair Value Disclosure [Member] | Municipal Bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 51,601 | 49,319 |
Estimate of Fair Value, Fair Value Disclosure [Member] | Corporate Bond Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 12,091 | 5,001 |
Fair Value, Inputs, Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Equity securities - mutual funds | 6,254 | 5,287 |
Derivative contracts, net | 0 | 0 |
Assets, fair value | 21,346 | 15,415 |
Fair Value, Inputs, Level 1 [Member] | U.S. Government-backed securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 15,092 | 10,128 |
Fair Value, Inputs, Level 1 [Member] | Agency bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 1 [Member] | Commercial paper [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 1 [Member] | Certificates of deposit [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 1 [Member] | Municipal Bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 1 [Member] | Corporate Bond Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 2 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Equity securities - mutual funds | 0 | 0 |
Derivative contracts, net | -2,936 | -1,113 |
Assets, fair value | 157,290 | 138,941 |
Fair Value, Inputs, Level 2 [Member] | U.S. Government-backed securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 2 [Member] | Agency bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 52,967 | 37,961 |
Fair Value, Inputs, Level 2 [Member] | Commercial paper [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 34,989 | 39,987 |
Fair Value, Inputs, Level 2 [Member] | Certificates of deposit [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 8,578 | 7,786 |
Fair Value, Inputs, Level 2 [Member] | Municipal Bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 51,601 | 49,319 |
Fair Value, Inputs, Level 2 [Member] | Corporate Bond Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 12,091 | 5,001 |
Fair Value, Inputs, Level 3 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Equity securities - mutual funds | 0 | 0 |
Derivative contracts, net | 0 | 0 |
Assets, fair value | 0 | 0 |
Fair Value, Inputs, Level 3 [Member] | U.S. Government-backed securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 3 [Member] | Agency bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 3 [Member] | Commercial paper [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 3 [Member] | Certificates of deposit [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 3 [Member] | Municipal Bonds [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | 0 | 0 |
Fair Value, Inputs, Level 3 [Member] | Corporate Bond Securities [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Available for sale marketable securities | $0 | $0 |