Product warranties (Provision for warranty obligations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Sep. 27, 2014	Sep. 28, 2013
Product Warranties Disclosures [Abstract]
Product warranty period, maximum			50 years
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 32,236	$ 33,674	$ 35,818	$ 32,930
Warranty claims paid during the period	(11,720)	(12,144)	(41,606)	(41,751)
Acquisitions	0	48	0	3,331
Warranty expense during the period	10,487	11,989	36,791	39,057
Balance at end of period	$ 31,003	$ 33,567	$ 31,003	$ 33,567