Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 27, 2014	Dec. 31, 2013
Assets:
Held-to-maturity Securities, Transferred Security, at Carrying Value	$ 0
Held-to-maturity Securities, Unrecognized Holding Gain	0
Other than Temporary Impairment Losses, Investments, Held-to-maturity Securities	0
Assets held in rabbi trusts	38,270	36,992
Available for sale securities	7,162	7,356
Fair Value Assets	45,432	44,348
Liabilities:
Embedded derivative	(1,076)	(1,037)
Fair Value Liabilities	(1,076)	(1,037)
Long-term Debt, Fair Value	859,500	750,700
Carrying value of long-term debt, excluding derivative liabilities	439,804	363,874
Derivative, Notional Amount	25,000
Derivative, Description of Terms	In the third fiscal quarter of 2014, the Company entered into a forward contract with a highly-rated financial institution to mitigate the foreign currency risk associated with an intercompany loan denominated in a currency other than the legal entity's functional currency. The notional amount of the forward contract was $25,000 as of September 27, 2014. The intercompany loan was used to finance a portion of the purchase price for Capella. The forward contract settles monthly and is expected to be renewed at the Company's discretion on a monthly basis until the intercompany loan is repaid. The forward contract was renewed on the last day of the third fiscal quarter. We have not designated the forward contract as a hedge for accounting purposes, and as such the change in the fair value of the contract is recognized in the consolidated condensed statements of operations as a component of other income (expense).
Fair Value, Inputs, Level 1 [Member]
Assets:
Assets held in rabbi trusts	25,081	24,064
Available for sale securities	7,162	7,356
Fair Value Assets	32,243	31,420
Liabilities:
Fair Value Liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Assets held in rabbi trusts	13,189	12,928
Available for sale securities	0	0
Fair Value Assets	13,189	12,928
Liabilities:
Fair Value Liabilities	0	0
Fair Value, Inputs, Level 3 [Member]
Assets:
Assets held in rabbi trusts	0	0
Available for sale securities	0	0
Fair Value Assets	0	0
Liabilities:
Fair Value Liabilities	(1,076)	(1,037)
Convertible Senior Debentures 2040 [Member]
Liabilities:
Embedded derivative	(553)	(491)
Convertible Senior Debentures 2040 [Member] | Fair Value, Inputs, Level 1 [Member]
Liabilities:
Embedded derivative	0	0
Convertible Senior Debentures 2040 [Member] | Fair Value, Inputs, Level 2 [Member]
Liabilities:
Embedded derivative	0	0
Convertible Senior Debentures 2040 [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities:
Embedded derivative	(553)	(491)
Convertible Senior Debentures 2041 [Member]
Liabilities:
Embedded derivative	(314)	(349)
Convertible Senior Debentures 2041 [Member] | Fair Value, Inputs, Level 1 [Member]
Liabilities:
Embedded derivative	0	0
Convertible Senior Debentures 2041 [Member] | Fair Value, Inputs, Level 2 [Member]
Liabilities:
Embedded derivative	0	0
Convertible Senior Debentures 2041 [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities:
Embedded derivative	(314)	(349)
Convertible Senior Debentures 2042 [Member]
Liabilities:
Embedded derivative	(209)	(197)
Convertible Senior Debentures 2042 [Member] | Fair Value, Inputs, Level 1 [Member]
Liabilities:
Embedded derivative	0	0
Convertible Senior Debentures 2042 [Member] | Fair Value, Inputs, Level 2 [Member]
Liabilities:
Embedded derivative	0	0
Convertible Senior Debentures 2042 [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities:
Embedded derivative	$ (209)	$ (197)