CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Non-controlling Interests [Member]	Total
Balance at Dec. 31, 2012	$ 4.7	$ 345.9	$ 1,032.9	$ (51.3)	$ (541.9)	$ 23.3	$ 813.6
Net income	0.0	0.0	80.3	0.0	0.0	3.1	83.4
Other comprehensive income (loss)	0.0	0.0	0.0	20.0	0.0	(1.7)	18.3
Dividends declared	0.0	0.0	(6.9)	0.0	0.0	0.0	(6.9)
Dividends to non-controlling interest	0.0	0.0	0.0	0.0	0.0	(2.4)	(2.4)
Capital contributions by non-controlling interests	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Purchase of common stock for treasury	0.0	0.0	0.0	0.0	(51.8)	0.0	(51.8)
Equity reclassification adjustment to non-controlling interests	0.0	(4.6)	0.0	0.0	0.0	4.6	0.0
Issuance of shares pursuant to employee stock compensation plans	0.0	12.2	0.0	0.0	0.0	0.0	12.2
Income tax benefit arising from employee stock compensation plans	0.0	2.8	0.0	0.0	0.0	0.0	2.8
Stock based compensation	0.0	5.2	0.0	0.0	0.0	0.0	5.2
Balance at Dec. 31, 2013	4.7	361.5	1,106.3	(31.3)	(593.7)	26.9	874.4
Net income	0.0	0.0	92.4	0.0	0.0	3.1	95.5
Other comprehensive income (loss)	0.0	0.0	0.0	(81.6)	0.0	(1.0)	(82.6)
Dividends declared	0.0	0.0	(6.9)	0.0	0.0	0.0	(6.9)
Dividends to non-controlling interest	0.0	0.0	0.0	0.0	0.0	(3.3)	(3.3)
Purchase of non-controlling interest shares	0.0	(2.1)	0.0	0.0	0.0	0.0	(2.1)
Acquisition of AMCOL	0.0	0.0	0.0	0.0	0.0	0.2	0.2
Issuance of shares pursuant to employee stock compensation plans	0.1	3.3	0.0	0.0	0.0	0.0	3.4
Income tax benefit arising from employee stock compensation plans	0.0	4.4	0.0	0.0	0.0	0.0	4.4
Stock based compensation	0.0	5.9	0.0	0.0	0.0	0.0	5.9
Balance at Dec. 31, 2014	4.8	373.0	1,191.8	(112.9)	(593.7)	25.9	888.9
Net income	0.0	0.0	107.9	0.0	0.0	3.7	111.6
Other comprehensive income (loss)	0.0	0.0	0.0	(68.0)	0.0	(1.3)	(69.3)
Dividends declared	0.0	0.0	(7.0)	0.0	0.0	0.0	(7.0)
Dividends to non-controlling interest	0.0	0.0	0.0	0.0	0.0	(1.1)	(1.1)
Issuance of shares pursuant to employee stock compensation plans	0.0	2.4	0.0	0.0	0.0	0.0	2.4
Income tax benefit arising from employee stock compensation plans	0.0	1.0	0.0	0.0	0.0	0.0	1.0
Stock based compensation	0.0	11.2	0.0	0.0	0.0	0.0	11.2
Balance at Dec. 31, 2015	$ 4.8	$ 387.6	$ 1,292.7	$ (180.9)	$ (593.7)	$ 27.2	$ 937.7