Goodwill and Other Intangible Assets - Gross carrying amount and accumulated amortization of the company's intangible assets other than goodwill (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Intangible asset balances by major asset class
Finite-lived Intangible assets, amortization amount	$ (49.3)	$ (45.3)
Intangible assets, gross (excluding goodwill)	171.4	159.4
Intangible assets, book value	122.1	114.1
Customer Relationships
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	10.7	10.3
Finite-lived Intangible assets, amortization amount	(8.7)	(7.8)
Finite-lived intangible assets, book value	2.0	2.5
Patents
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	30.6	28.5
Finite-lived Intangible assets, amortization amount	(29.7)	(27.4)
Finite-lived intangible assets, book value	0.9	1.1
Engineering Drawings
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	10.8	10.0
Finite-lived Intangible assets, amortization amount	(10.7)	(9.9)
Finite-lived intangible assets, book value	0.1	0.1
Distribution Network
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	19.5	18.0
Finite-lived Intangible assets, amortization amount	(0.1)	0.0
Finite-lived intangible assets, book value	19.4	18.0
Other Intangibles
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	0.1	0.2
Finite-lived Intangible assets, amortization amount	(0.1)	(0.2)
Finite-lived intangible assets, book value	0.0	0.0
Trademarks and Tradenames
Intangible asset balances by major asset class
Indefinite-lived intangible assets, book value	$ 99.7	$ 92.4