Fair Value of Assets and Liabilities - Securities (Details) (Fair Value, Measurements, Recurring [Member], USD $) | Jun. 29, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Fair Value, Inputs, Level 1 [Member] | ' | ' |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | ' |
Equity securities - mutual funds | $6,680 | $5,287 |
Derivative contracts, net | 0 | 0 |
Assets, fair value | 21,743 | 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 | 15,063 | 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 | -2,932 | -1,113 |
Assets, fair value | 158,913 | 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 | 37,481 | 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 | 45,824 | 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 | 13,663 | 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 | 49,929 | 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 | 14,948 | 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 |
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 | 6,680 | 5,287 |
Derivative contracts, net | -2,932 | -1,113 |
Assets, fair value | 180,656 | 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 | 15,063 | 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 | 37,481 | 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 | 45,824 | 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 | 13,663 | 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 | 49,929 | 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 | $14,948 | $5,001 |