Goodwill and Other Intangible Assets - Gross carrying amount and accumulated amortization of the company's intangible assets other than goodwill (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Intangible asset balances by major asset class
Finite-lived intangible assets, amortization amount	$ (50.0)	$ (49.3)
Intangible assets, gross (excluding goodwill)	173.7	171.4
Intangible assets, book value	123.7	122.1
Customer Relationships
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	10.6	10.7
Finite-lived intangible assets, amortization amount	(8.7)	(8.7)
Finite-lived intangible assets, book value	1.9	2.0
Patents
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	31.2	30.6
Finite-lived intangible assets, amortization amount	(30.1)	(29.7)
Finite-lived intangible assets, book value	1.1	0.9
Engineering Drawings
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	10.9	10.8
Finite-lived intangible assets, amortization amount	(10.9)	(10.7)
Finite-lived intangible assets, book value	0.0	0.1
Distribution Network
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	19.8	19.5
Finite-lived intangible assets, amortization amount	(0.2)	(0.1)
Finite-lived intangible assets, book value	19.6	19.4
Other Intangibles
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	0.1	0.1
Finite-lived intangible assets, amortization amount	(0.1)	(0.1)
Trademarks and Tradenames
Intangible asset balances by major asset class
Indefinite-lived intangible assets, book value	$ 101.1	$ 99.7