Severance, impairment and other associated costs (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 30, 2011	Dec. 31, 2010	Dec. 25, 2009
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 14.7	$ 2.7	$ 11.9
Severance and related costs	13.7	1.9	3.0
Write-downs of fixed assets no longer in use	0.8	0.8	8.9
Employees severed			320
Impaired goodwill and identifiable intangible assets		29.7	71.0
Other associated costs			0.3
Write-down of a manufacturing facility to its fair value	0.2
Restructuring Reserve [Roll Forward]
Balance accrued at beginning of period	0.6	1.4	7.8
Net expense during the period ended	13.7	1.9	3.0
Severance payments	(9.6)	(2.1)	(7.3)
Other associated costs	(0.5)	(0.5)	(0.5)
Currency translation adjustments		(0.1)	(1.6)
Balance accrued at end of period	4.2	0.6	1.4
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Impaired identifiable intangible assets		3.6
North America Corporate Headquarters [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3.5
Severance and related costs		0.5
Employees severed	30
Chinese Manufacturing plants [Member]
Restructuring Cost and Reserve [Line Items]
Severance and related costs	6.3	1.0
Write-downs of fixed assets no longer in use	0.8
Employees severed	2,400	530
Write-down of a manufacturing facility to its fair value	0.2
Wireless Audio Components [Member]
Restructuring Cost and Reserve [Line Items]
Severance and related costs		1.9	3.0
Write-downs of fixed assets no longer in use		0.8
Number of properties disposed of related to cost reductions			2
Impaired goodwill and identifiable intangible assets		29.7	71.0
Transfer of Operations To China [Member]
Restructuring Cost and Reserve [Line Items]
Severance and related costs		0.2	1.0
Employees severed			45
Adjustment to prior period severance benefit accrual to reflect final benefit projections			(0.6)
Other associated costs			1.6
Finland [Member]
Restructuring Cost and Reserve [Line Items]
Severance and related costs		$ 0.6
Employees severed		40