Non-controlling interests (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended			6 Months Ended
	May 31, 2014	Jun. 29, 2014		Jun. 30, 2013	Jun. 29, 2014		Jun. 30, 2013
Noncontrolling Interest [Line Items]
Balance					$ 874.4	[1]
Net income		19.4		17.7	35.6		37.3
Other Comprehensive Income		4.5		(5.9)	7.4		(18.3)
Dividends declared					(3.5)
Dividends to non-controlling interest					(3.3)		(0.8)
Purchase of non-controlling interest share	(2.0)				(2.1)		0
Issuance of shares pursuant to employee stock compensation plans					2.6
Income tax benefit arising from employee stock compensation plans					1.2
Stock based compensation					1.8
Balance		914.1	[2]		914.1	[2]
Percentage of noncontrolling acquired during the period (in hundredths)	20.00%
Payments to noncontrolling interests	2.0				2.1		0
Adjustments to net income attributable to MTI [Abstract]
Net income attributable to Minerals Technologies Inc. (MTI)		18.5		17.1	34.1		35.9
Transfer from non-controlling interest [Abstract]
Decrease in additional paid-in capital for purchase of the remaining non-controlling interest in CETCO India		(2.1)		0	(2.1)		0
Change from net income attributable to MTI and transfers from non-controlling interest		16.4		17.1	32.0		35.9
Common Stock [Member]
Noncontrolling Interest [Line Items]
Balance					4.7
Net income					0
Other Comprehensive Income					0
Dividends declared					0
Dividends to non-controlling interest					0
Purchase of non-controlling interest share					0
Issuance of shares pursuant to employee stock compensation plans					0.1
Income tax benefit arising from employee stock compensation plans					0
Stock based compensation					0
Balance		4.8			4.8
Payments to noncontrolling interests					0
Additional Paid-in Capital [Member]
Noncontrolling Interest [Line Items]
Balance					361.5
Net income					0
Other Comprehensive Income					0
Dividends declared					0
Dividends to non-controlling interest					0
Purchase of non-controlling interest share					(2.1)
Issuance of shares pursuant to employee stock compensation plans					2.5
Income tax benefit arising from employee stock compensation plans					1.2
Stock based compensation					1.8
Balance		364.9			364.9
Payments to noncontrolling interests					2.1
Retained Earnings [Member]
Noncontrolling Interest [Line Items]
Balance					1,106.3
Net income					34.1
Other Comprehensive Income					0
Dividends declared					(3.5)
Dividends to non-controlling interest					0
Purchase of non-controlling interest share					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		1,136.9			1,136.9
Payments to noncontrolling interests					0
Accumulated Other Comprehensive Income (Loss) [Member]
Noncontrolling Interest [Line Items]
Balance					(31.3)
Net income					0
Other Comprehensive Income					7.7
Dividends declared					0
Dividends to non-controlling interest					0
Purchase of non-controlling interest share					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		(23.6)			(23.6)
Payments to noncontrolling interests					0
Treasury Stock [Member]
Noncontrolling Interest [Line Items]
Balance					(593.7)
Net income					0
Other Comprehensive Income					0
Dividends declared					0
Dividends to non-controlling interest					0
Purchase of non-controlling interest share					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)			(593.7)
Payments to noncontrolling interests					0
Noncontrolling Interests [Member]
Noncontrolling Interest [Line Items]
Balance					26.9
Net income					1.5
Other Comprehensive Income					(0.3)
Dividends declared					0
Dividends to non-controlling interest					(3.3)
Purchase of non-controlling interest share					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		24.8			24.8
Payments to noncontrolling interests					$ 0

[1] Condensed from audited financial statements

[2] Unaudited