Severance, impairment and other associated costs (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 28, 2014	Mar. 29, 2013
Restructuring Reserve [Roll Forward]
Balance accrued at beginning of period	$ 0.5
Net expense	1.0
Cash payments	(0.4)
Non-cash charges	0
Balance accrued at end of period	1.1
Restructuring and impairment charges	1.0	0.1
Severance and related costs	1.0
Estimation of remaining cost	1.2
Expect to achieve annualized cost	9.0
Accrual for restructuring actions	$ 1.1