Fair Value of Financial Instruments (Details) (USD $) | Sep. 27, 2014 | Dec. 28, 2013 |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | $55,838,000 | ' |
Asset measured at, fair value | 55,232,000 | ' |
Recurring [Member] | ' | ' |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | 55,838,000 | 38,917,000 |
Assets measured at fair value, Unrealized gains | 179,000 | 284,000 |
Assets measured at fair value, Unrealized losses | -785,000 | -472,000 |
Asset measured at, fair value | 55,232,000 | 38,729,000 |
Level 1 [Member] | Recurring [Member] | ' | ' |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | 12,091,000 | 5,914,000 |
Assets measured at fair value, Unrealized gains | 158,000 | 156,000 |
Assets measured at fair value, Unrealized losses | -220,000 | -65,000 |
Asset measured at, fair value | 12,029,000 | 6,005,000 |
Liabilities | ' | ' |
Liabilities measured at fair value, Adjusted cost | ' | 38,000 |
Liabilities measured at fair value, Unrealized gains | 0 | 0 |
Liabilities measured at fair value, Unrealized losses | 0 | 0 |
Liabilities measured at fair value | 65,000 | 38,000 |
Convertible Debt, Fair Value Disclosures | 65,000 | ' |
Level 1 [Member] | Phantom stock units [Member] | Recurring [Member] | ' | ' |
Liabilities | ' | ' |
Liabilities measured at fair value, Adjusted cost | 65,000 | 38,000 |
Liabilities measured at fair value, Unrealized gains | 0 | 0 |
Liabilities measured at fair value, Unrealized losses | 0 | 0 |
Liabilities measured at fair value | 65,000 | 38,000 |
Level 1 [Member] | Equity securities [Member] | Recurring [Member] | ' | ' |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | 1,827,000 | 2,049,000 |
Assets measured at fair value, Unrealized gains | 124,000 | 137,000 |
Assets measured at fair value, Unrealized losses | -178,000 | -64,000 |
Asset measured at, fair value | 1,773,000 | 2,122,000 |
Level 1 [Member] | Mutual funds [Member] | Recurring [Member] | ' | ' |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | 10,264,000 | 3,865,000 |
Assets measured at fair value, Unrealized gains | 34,000 | 19,000 |
Assets measured at fair value, Unrealized losses | -42,000 | -1,000 |
Asset measured at, fair value | 10,256,000 | 3,883,000 |
Level 2 [Member] | Recurring [Member] | ' | ' |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | 43,747,000 | 33,003,000 |
Assets measured at fair value, Unrealized gains | 21,000 | 128,000 |
Assets measured at fair value, Unrealized losses | -565,000 | -407,000 |
Asset measured at, fair value | 43,203,000 | 32,724,000 |
Level 2 [Member] | Corporate fixed income [Member] | Recurring [Member] | ' | ' |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | 39,019,000 | 25,240,000 |
Assets measured at fair value, Unrealized gains | 21,000 | 126,000 |
Assets measured at fair value, Unrealized losses | -469,000 | -250,000 |
Asset measured at, fair value | 38,571,000 | 25,116,000 |
Level 2 [Member] | Municipal bonds [Member] | Recurring [Member] | ' | ' |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | 3,790,000 | 2,775,000 |
Assets measured at fair value, Unrealized gains | 0 | 1,000 |
Assets measured at fair value, Unrealized losses | -29,000 | -28,000 |
Asset measured at, fair value | 3,761,000 | 2,748,000 |
Level 2 [Member] | Certificates of deposit [Member] | Recurring [Member] | ' | ' |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | ' | 4,014,000 |
Assets measured at fair value, Unrealized gains | ' | 1,000 |
Assets measured at fair value, Unrealized losses | ' | 0 |
Asset measured at, fair value | ' | 4,015,000 |
Level 2 [Member] | Asset backed securities [Member] | Recurring [Member] | ' | ' |
Assets | ' | ' |
Assets measured at fair value, Adjusted cost | 887,000 | 974,000 |
Assets measured at fair value, Unrealized gains | 0 | 0 |
Assets measured at fair value, Unrealized losses | -67,000 | -129,000 |
Asset measured at, fair value | $820,000 | $845,000 |