Step Acquisition (Details) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 28, 2014 USD ($)	Mar. 29, 2014 USD ($) company	Jun. 30, 2015 USD ($) company	Jun. 28, 2014 USD ($)	Dec. 31, 2014 USD ($)
Spanish companies
Number of Spanish companies | company				2
Provision for income taxes	$ 3,735	$ 4,305		$ 8,069	$ 11,642
Spanish companies
Spanish companies
Number of Spanish companies | company			2
Ownership interest in Spanish companies after step acquisition (as a percent)			50.00%			83.00%
Net loss related to acquired companies			$ 529
Provision for income taxes			$ 2,350
Amount of subscription for common shares						$ 1,400
Payment for purchase of stock						$ 1,200