Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Millions		12 Months Ended
Dec. 22, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax expense at federal rate		35.00%	35.00%	35.00%
Increase (decrease) resulting from:
Reduction of statutory federal rate (a)		(8.00%)	0.00%	0.00%
State tax, net of federal income tax benefit		1.60%	1.10%	1.00%
Provision for uncertain federal and state tax matters		0.00%	0.00%	0.90%
Tax credits		(1.30%)	(0.60%)	(0.50%)
Other		0.00%	0.00%	(0.10%)
Effective tax rate		27.30%	35.50%	36.30%
Income tax benefit as result of the Tax Cuts and Jobs Act of 2017	$ 19.3	$ 19.3

Increase (decrease) resulting from: [Abstract]

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Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)

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

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income tax contingencies. Includes, but not limited to, domestic tax contingency, foreign tax contingency, state and local tax contingency, and other contingencies.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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