Debt - Long-Term Debt - (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 28, 2015	Jun. 28, 2015	Dec. 31, 2014
Long-term debt
Revolving credit facility due in 2017	$ 88,700	$ 88,700	$ 75,000
Amortization expenses	50	100
Revolving credit facility due in 2017 | Line of Credit
Long-term debt
Revolving credit facility due in 2017	$ 88,700	$ 88,700	$ 75,000
Weighted-average interest rate	1.40%	1.40%	1.50%
Amount available	$ 108,985	$ 108,985	$ 122,535
Total credit facility	200,000	200,000	200,000
Standby letters of credit	$ 2,315	$ 2,315	$ 2,465
Commitment fee percentage per annum		0.25%	0.25%