Accounts Receivable, Net and Supplemental Balance-Sheet and Operating Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2015	Sep. 27, 2014	Oct. 03, 2015	Sep. 27, 2014	Dec. 31, 2014
Accounts receivable, net
Accounts receivable	$ 109,895		$ 109,895		$ 98,657
Receivables under contractual arrangements	28,773		28,773		15,362
Accounts receivable, gross	138,668		138,668		114,019
Less allowances for doubtful accounts	3,100		3,100		2,421
Accounts receivable, net	135,568		135,568		111,598
Accrued expenses
Employee compensation	20,268		20,268		19,195
Accrued compensated absences	9,002		9,002		8,034
Self-insured medical claims	1,450		1,450		2,722
Customer advances, deposits	782		782		2,030
Taxes, other than income	3,140		3,140		2,054
Other	357		357		890
Total	34,999		34,999		34,925
Other current liabilities
Other current liabilities	43,248		43,248		$ 31,288
Other Nonoperating Income (Expense) [Abstract]
Other income (expense), net	(2,068)	$ (1,112)	(3,776)	$ (2,417)
Foreign currency losses included in other nonoperating expense, net	$ (367)	$ (126)	$ (464)	$ (78)