Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Accrued expenses	$ 3.4	$ 3.2
Accounts receivable	1.0	1.2
Net operating loss carryforward	116.7	123.6
Stock-based compensation	1.8	2.1
Intangible assets	8.0	8.0
Credits	1.0	1.0
Property and equipment	0.4	0.3
Other	2.5	2.9
Deferred Tax Assets Gross	134.8	142.3
Valuation allowance		(1.2)
Net deferred tax assets	134.8	141.1
Deferred tax liabilities:
Intangible assets	(89.6)	(82.5)
Deferred state taxes	(0.5)	(0.7)
Net deferred tax liabilities	(90.1)	(83.2)
Deferred Assets Liabilities Net	$ 44.7	$ 57.9