Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Allowance for doubtful accounts	$ 6.4	$ 5.6
Accrued expenses	0.0	1.2
Accrued bonus	4.0	0.0
Workers' compensation	9.8	8.1
Amortization of intangible assets	(72.2)	(89.2)
Share-based compensation	5.0	3.3
Net operating loss carryforwards	48.5	59.3
Tax credit carryforwards	4.7	2.6
Other	5.1	1.8
Gross deferred tax assets	155.7	171.1
Valuation Allowance	0.3	0.6
Net deferred tax assets	155.4	170.5
Property and equipment	9.5	31.3
Deferred revenue	(18.5)	(16.8)
Other liabilities	2.2	0.0
Gross deferred tax (liabilities)	30.2	48.1
Net deferred tax assets (liabilities)	$ 125.2	$ 122.4