Product warranties (Provision for warranty obligations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014	Jun. 29, 2013
Product Warranties Disclosures [Abstract]
Product warranty period, maximum			50 years
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 33,260	$ 35,483	$ 35,818	$ 32,930
Warranty claims paid during the period	(15,862)	(16,306)	(29,886)	(29,607)
Product Warranty Accrual, Additions from Business Acquisition	0	503	0	3,283
Warranty expense during the period	14,837	13,994	26,303	27,068
Balance at end of period	$ 32,235	$ 33,674	$ 32,235	$ 33,674