Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Statement of Cash Flows [Abstract]
Proceeds from Sale and Maturity of Marketable Securities	$ 3.7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	120.3	$ 132.4	$ 125.4	$ 151.6
Operating Activities
Net Income (Loss) Attributable to Parent	80.2	38.2
Net (loss) income attributable to noncontrolling interest	0.3	(0.1)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	35.8	32.9
Loss on sale of assets	0.6	0.1
Deferred income tax provision	(0.2)	1.5
Stock-based compensation expense	10.3	5.6
Pension and other postretirement expense	2.0	7.2
Pension contributions and other postretirement benefit payments	(6.1)	(6.1)
Changes in operating assets and liabilities:
Accounts receivable	(72.1)	(50.3)
Increase (Decrease) in Unbilled Receivables	(11.5)	0.0
Inventories	(53.8)	(6.5)
Accounts payable, trade	(2.3)	48.6
Other accrued expenses	(38.7)	(28.4)
Income taxes	13.6	6.7
Other, net	(2.4)	(2.7)
Net Cash Provided by Operating Activities	(44.3)	46.7
Investing Activities
Capital expenditures	(17.8)	(19.3)
Acquisitions, net of cash received	0.0	0.6
Proceeds from disposals of property, plant and equipment	0.1	0.1
Common Stock, Value, Outstanding		(6.8)
Other	0.0	(0.3)
Net Cash Used by Investing Activities	(14.0)	(26.9)
Financing Activities
Cash dividends paid to shareholders	(21.1)	(20.3)
Purchase of treasury shares	(22.7)	(8.1)
Net proceeds from common share activity	8.4	16.6
Payments Related to Tax Withholding for Share-based Compensation	4.4	8.2
Proceeds from Accounts Receivable Securitization	51.0	23.1
Repayments of Accounts Receivable Securitization	15.0	10.0
Proceeds from Issuance of Long-term Debt	75.0	48.5
Payments on long-term debt	(42.4)	(90.3)
Short-term debt activity, net	24.6	5.8
Proceeds from (Payments for) Other Financing Activities	(1.1)	0.0
Net Cash Used by Financing Activities	52.3	(42.9)
Effect of exchange rate changes on cash	0.9	3.9
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	(5.1)	$ (19.2)
Cash and cash equivalents beginning of period	121.6
Cash and cash equivalents end of period	$ 116.4		$ 121.6