Consolidated Statements of Income (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]
Net sales	$ 221.3	$ 185.0	$ 442.0	$ 384.4
Cost of goods sold	(152.7)	(125.6)	(307.7)	(261.2)
Gross profit	68.6	59.4	134.3	123.2
Operating expenses:
Selling, general and administrative	(37.7)	(31.5)	(79.7)	(67.2)
Research and development	(5.6)	(5.3)	(11.3)	(10.9)
Impairment of Octane Additives segment goodwill	0	(0.3)	0	(0.6)
Total operating expenses	(43.3)	(37.1)	(91.0)	(78.7)
Operating income	25.3	22.3	43.3	44.5
Other net income/(expense)	(0.7)	(1.0)	1.2	0
Interest expense	(0.9)	(0.5)	(1.9)	(0.9)
Interest income	0.1	0.1	0.2	0.2
Income before income taxes	23.8	20.9	42.8	43.8
Income taxes	(5.3)	(3.8)	(7.4)	(8.7)
Net income	$ 18.5	$ 17.1	$ 35.4	$ 35.1
Earnings per share:
Basic	$ 0.76	$ 0.73	$ 1.45	$ 1.50
Diluted	$ 0.75	$ 0.71	$ 1.44	$ 1.46
Weighted average shares outstanding (in thousands):
Basic	24,401	23,528	24,382	23,466
Diluted	24,672	24,057	24,632	24,073