Goodwill and Other Intangible Assets - Gross carrying amount and accumulated amortization of the company's intangible assets other than goodwill (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Intangible asset balances by major asset class
Intangible assets, gross (excluding goodwill)	$ 168.1	$ 171.4
Finite-lived intangible assets, amortization amount	(48.4)	(49.3)
Intangible assets, book value	119.7	122.1
Customer Relationships
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	10.2	10.7
Finite-lived intangible assets, amortization amount	(8.4)	(8.7)
Finite-lived intangible assets, book value	1.8	2.0
Patents
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	30.2	30.6
Finite-lived intangible assets, amortization amount	(29.2)	(29.7)
Finite-lived intangible assets, book value	1.0	0.9
Engineering Drawings
Intangible asset balances by major asset class
Finite-lived intangible assets, carrying amount	10.7	10.8
Finite-lived intangible assets, amortization amount	(10.6)	(10.7)
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	19.2	19.5
Finite-lived intangible assets, amortization amount	(0.1)	(0.1)
Finite-lived intangible assets, book value	19.1	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	$ 97.7	$ 99.7