Non-controlling interests (Details) - USD ($) $ in Millions		3 Months Ended
		Apr. 01, 2018	Apr. 02, 2017
Noncontrolling Interest [Line Items]
Balance	[1]	$ 1,279.1
Net income		41.1	$ 35.6
Other comprehensive income		18.7	$ 14.3
Dividends declared		(1.8)
Dividends to non-controlling interest		(0.2)
Issuance of shares pursuant to employee stock compensation plans		0.5
Stock based compensation		0.0
Purchase of treasury stock		(5.7)
Balance	[2]	1,331.8
Common Stock [Member]
Noncontrolling Interest [Line Items]
Balance		4.9
Net income		0.0
Other comprehensive income		0.0
Dividends declared		0.0
Dividends to non-controlling interest		0.0
Issuance of shares pursuant to employee stock compensation plans		0.0
Stock based compensation		0.0
Purchase of treasury stock		0.0
Balance		4.9
Additional Paid-in Capital [Member]
Noncontrolling Interest [Line Items]
Balance		422.7
Net income		0.0
Other comprehensive income		0.0
Dividends declared		0.0
Dividends to non-controlling interest		0.0
Issuance of shares pursuant to employee stock compensation plans		0.5
Stock based compensation		0.0
Purchase of treasury stock		0.0
Balance		423.2
Retained Earnings [Member]
Noncontrolling Interest [Line Items]
Balance		1,607.2
Net income		39.9
Other comprehensive income		0.0
Dividends declared		(1.8)
Dividends to non-controlling interest		0.0
Issuance of shares pursuant to employee stock compensation plans		0.0
Stock based compensation		0.0
Purchase of treasury stock		0.0
Balance		1,645.3
Accumulated Other Comprehensive Income (Loss) [Member]
Noncontrolling Interest [Line Items]
Balance		(186.1)
Net income		0.0
Other comprehensive income		18.2
Dividends declared		0.0
Dividends to non-controlling interest		0.0
Issuance of shares pursuant to employee stock compensation plans		0.0
Stock based compensation		0.0
Purchase of treasury stock		0.0
Balance		(167.9)
Treasury Stock [Member]
Noncontrolling Interest [Line Items]
Balance		(597.0)
Net income		0.0
Other comprehensive income		0.0
Dividends declared		0.0
Dividends to non-controlling interest		0.0
Issuance of shares pursuant to employee stock compensation plans		0.0
Stock based compensation		0.0
Purchase of treasury stock		(5.7)
Balance		(602.7)
Non-controlling Interests [Member]
Noncontrolling Interest [Line Items]
Balance		27.4
Net income		1.2
Other comprehensive income		0.5
Dividends declared		0.0
Dividends to non-controlling interest		(0.2)
Issuance of shares pursuant to employee stock compensation plans		0.0
Stock based compensation		0.0
Purchase of treasury stock		0.0
Balance		$ 29.0

[1] Condensed from audited financial statements

[2] Unaudited