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 |