Income Taxes (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) States	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Income Tax Disclosure [Line Items]
Income tax receivable		$ 0.5	$ 15.0
Valuation Allowance		0.3	0.6
Net change in total valuation allowance		(0.3)	0.3
Uncertain tax benefits accrued		4.7	4.0	$ 3.9
Interest and penalties recognized related to uncertain income tax positions		0.2	0.1
Interest and penalties accrued related to uncertain income tax positions		$ 0.2	0.2
Number of individual states subject to income taxes | States		50
Unrecognized Tax Benefits Period Increase Decrease	$ (0.6)
Net Operating Loss [Member]
Income Tax Disclosure [Line Items]
Uncertain tax benefits accrued		$ 3.1	3.1
Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Uncertain tax benefits accrued		0.7	$ 0.3
Research And Development Tax Credit [Member]
Income Tax Disclosure [Line Items]
Tax credits		1.9
Employment Tax Credit [Member]
Income Tax Disclosure [Line Items]
Tax credits		0.4
Alternative Minimum Tax Credit [Member]
Income Tax Disclosure [Line Items]
Tax credits		1.0
State Tax Credit [Member]
Income Tax Disclosure [Line Items]
Tax credits		3.1
Other Long Term Obligations [Member]
Income Tax Disclosure [Line Items]
Uncertain tax benefits accrued		0.7
Deferred Income Taxes [Member]
Income Tax Disclosure [Line Items]
Uncertain tax benefits accrued		3.8
Accrued Expenses [Member]
Income Tax Disclosure [Line Items]
Uncertain tax benefits accrued		$ 0.2
Minimum [Member]
Income Tax Disclosure [Line Items]
Tax years open to examination		2001
Maximum [Member]
Income Tax Disclosure [Line Items]
Tax years open to examination		2015
State and Local Jurisdiction [Member] | Net Operating Loss [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		$ 254.3
Federal [Member]
Income Tax Disclosure [Line Items]
Income tax receivable		14.3
Net operating loss carryforwards		$ 116.3