Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income tax expense	$ 6.5	$ 7.5	$ 18.9	$ 17.4
Increase in tax expense attributable to change in state tax rate in Illinois				$ 0.6
Excess tax benefit from stock compensation activity			$ 0.6
Effective tax rate	23.00%	37.50%	23.50%	35.80%
2017 Tax Act transition tax, rate applied to cash	15.50%		15.50%
2017 Tax Act transition tax, rate applied to earnings in excess of cash	8.00%		8.00%

Increase in tax expense during the period attributable to the change in state tax rate in Illinois.

No definition available.

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- Definition

The tax rate applied to cash and equivalents at controlled foreign corporations for the untaxed post-1986 accumulated earnings and profits taxed under the Tax Cuts and Jobs Act of 2017 ("2017 Tax Act").

+ References

No definition available.

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The tax rate applied to earnings in excess of cash and equivalents at controlled foreign corporations for the untaxed post-1986 accumulated earnings and profits taxed under the Tax Cuts and Jobs Act of 2017 ("2017 Tax Act").

+ References

No definition available.

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- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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