Debt (Textuals) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Long-term debt, excluding current portion	$ 255.0	$ 196.0
Interest expense	9.4	9.3	$ 10.5
Aggregate annual maturities of long-term debt [Abstract]
2021	2.3
2022	44.3
2023	2.3
2024	133.8
Thereafter	73.0
Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months	$ 2.3
Senior A Notes Due 2022 [Member]
Line of Credit Facility [Line Items]
Debt instrument, maturity date	Jul. 05, 2022
Debt instrument, stated interest rate	3.67%
Senior B Notes Due 2024 [Member]
Line of Credit Facility [Line Items]
Debt instrument, maturity date	Jul. 05, 2024
Debt instrument, stated interest rate	3.82%
Senior C Notes Due 2027 [Member]
Line of Credit Facility [Line Items]
Debt instrument, maturity date	Jul. 05, 2027
Debt instrument, stated interest rate	4.02%
Revolving credit facility, due 2020 [Member]
Line of Credit Facility [Line Items]
Long-term debt, gross		$ 28.6
Senior Notes [Member]
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 168.0
Weighted average of the coupon interest rate	3.87%
Debt issuance costs	0.5 million	0.6 million
Senior Notes [Member] | Senior A Notes Due 2022 [Member]
Line of Credit Facility [Line Items]
Long-term debt, gross		$ 42.0
Debt instrument, face amount	$ 42.0
Debt instrument, stated interest rate	3.67%
Senior Notes [Member] | Senior B Notes Due 2024 [Member]
Line of Credit Facility [Line Items]
Long-term debt	$ 53.0
Long-term debt, gross		53.0
Debt instrument, face amount	$ 53.0
Debt instrument, stated interest rate	3.82%
Senior Notes [Member] | Senior C Notes Due 2027 [Member]
Line of Credit Facility [Line Items]
Long-term debt	$ 73.0
Long-term debt, gross		73.0
Debt instrument, face amount	$ 73.0
Debt instrument, stated interest rate	4.02%
Revolving credit facility, due 2024 [Domain]
Line of Credit Facility [Line Items]
Line of Credit Facility, current borrowing capacity	$ 300.0
Line of Credit Facility, additional borrowing capacity	350.0
Credit available for the issuance of letters of credit	30.0
Line of credit, noncurrent	0.0
Line of Credit Facility, unused commitment level	297.5
Debt issuance costs	1.1	$ 0.6
Term Loan Due 2024 [Member]
Line of Credit Facility [Line Items]
Long-term debt, current portion	2.3
Debt issuance costs	0.2
Long-term debt, gross	90.0
Debt instrument, face amount	$ 90.0
Debt instrument, stated interest rate	2.78%
Long-term debt, excluding current portion	$ 87.7
London Interbank Offered Rate (LIBOR) [Member] | Revolving credit facility, due 2024 [Domain]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	1.00%
London Interbank Offered Rate (LIBOR) [Member] | Term Loan Due 2024 [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	87.50%
Letter of Credit [Member] | Revolving credit facility, due 2024 [Domain]
Line of Credit Facility [Line Items]
Outstanding amount	$ 2.5
Domestic Line of Credit [Member] | Revolving credit facility, due 2024 [Domain]
Line of Credit Facility [Line Items]
Credit Facility is available for swing-line loans	30.0
Foreign Line of Credit [Member] | Revolving credit facility, due 2024 [Domain]
Line of Credit Facility [Line Items]
Credit Facility is available for swing-line loans	$ 20.0
Fed Funds Effective Rate Overnight Index Swap Rate [Member] | Revolving credit facility, due 2024 [Domain]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	50.00%
Minimum [Member] | Revolving credit facility, due 2024 [Domain]
Aggregate annual maturities of long-term debt [Abstract]
Ratio of debt to EBITDA	3.5
Minimum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	0.00%
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Revolving credit facility, due 2024 [Domain]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	8750.00%
Maximum [Member] | Revolving credit facility, due 2024 [Domain]
Aggregate annual maturities of long-term debt [Abstract]
Ratio of debt to EBITDA	4.0
Maximum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	3750.00%
Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Revolving credit facility, due 2024 [Domain]
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	13750.00%