Non-controlling interests (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 29, 2015		Mar. 30, 2014
Noncontrolling Interest [Line Items]
Balance	$ 888.9	[1]
Net income	36.0		16.3
Other comprehensive income (loss)	(26.4)		2.8
Dividends declared	(1.8)
Dividends to non-controlling interest	(0.2)		(0.3)
Issuance of shares pursuant to employee stock compensation plans	0.7
Income tax benefit arising from employee stock compensation plans	0.5
Stock based compensation	1.3
Balance	899.0	[2]
Common Stock [Member]
Noncontrolling Interest [Line Items]
Balance	4.8
Net income	0
Other comprehensive income (loss)	0
Dividends declared	0
Dividends to non-controlling interest	0
Issuance of shares pursuant to employee stock compensation plans	0
Income tax benefit arising from employee stock compensation plans	0
Stock based compensation	0
Balance	4.8
Additional Paid-in Capital [Member]
Noncontrolling Interest [Line Items]
Balance	373.0
Net income	0
Other comprehensive income (loss)	0
Dividends declared	0
Dividends to non-controlling interest	0
Issuance of shares pursuant to employee stock compensation plans	0.7
Income tax benefit arising from employee stock compensation plans	0.5
Stock based compensation	1.3
Balance	375.5
Retained Earnings [Member]
Noncontrolling Interest [Line Items]
Balance	1,191.8
Net income	35.1
Other comprehensive income (loss)	0
Dividends declared	(1.8)
Dividends to non-controlling interest	0
Issuance of shares pursuant to employee stock compensation plans	0
Income tax benefit arising from employee stock compensation plans	0
Stock based compensation	0
Balance	1,225.1
Accumulated Other Comprehensive Income (Loss) [Member]
Noncontrolling Interest [Line Items]
Balance	(112.9)
Net income	0
Other comprehensive income (loss)	(26.5)
Dividends declared	0
Dividends to non-controlling interest	0
Issuance of shares pursuant to employee stock compensation plans	0
Income tax benefit arising from employee stock compensation plans	0
Stock based compensation	0
Balance	(139.4)
Treasury Stock [Member]
Noncontrolling Interest [Line Items]
Balance	(593.7)
Net income	0
Other comprehensive income (loss)	0
Dividends declared	0
Dividends to non-controlling interest	0
Issuance of shares pursuant to employee stock compensation plans	0
Income tax benefit arising from employee stock compensation plans	0
Stock based compensation	0
Balance	(593.7)
Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Balance	25.9
Net income	0.9
Other comprehensive income (loss)	0.1
Dividends declared	0
Dividends to non-controlling interest	(0.2)
Issuance of shares pursuant to employee stock compensation plans	0
Income tax benefit arising from employee stock compensation plans	0
Stock based compensation	0
Balance	$ 26.7

[1] Condensed from audited financial statements

[2] Unaudited