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CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unrealized net (loss) gain on cash flow derivative instruments, related income tax benefit (provision)	$ 0.7	$ 0.6	$ (0.2)
Change in pension liability, related income tax (provision) benefit	(7.5)	5.7	(0.5)
Accumulated Other Comprehensive Loss
Unrealized net (loss) gain on cash flow derivative instruments, related income tax benefit (provision)	0.7	0.6	(0.2)
Change in pension liability, related income tax (provision) benefit	$ (7.5)	$ 5.7	$ (0.5)
Treasury Stock
Exercise of stock options, shares surrendered as proceeds and to pay taxes	160,856	54,019	418,754

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=96868048&loc=SL4569616-111683

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-Publisher FASB
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-Topic 220
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-Section 45
-Paragraph 10A
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-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580

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-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

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