Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Accrued expenses	$ 1.8	$ 3.4
Accounts receivable	0.6	1.0
Net operating loss carryforward	77.6	116.7
Stock-based compensation	0.9	1.8
Intangible assets		8.0
Credits	0.7	1.0
Property and equipment		0.4
Deferred state taxes	2.3
Other	1.4	2.5
Net deferred tax assets	85.3	134.8
Deferred tax liabilities:
Intangible assets	(57.3)	(89.6)
Property and equipment	(0.2)
Deferred state taxes		(0.5)
Tax gain deferral - FCC auction for broadcast spectrum	(68.6)
Net deferred tax liabilities	(126.1)	(90.1)
Deferred Liabilities Net	$ (40.8)
Deferred Assets Net		$ 44.7