Employee Retirement Plans - Schedule of Estimated Amount that will be Amortized from Accumulated Other Comprehensive Loss into Net Periodic Benefit Cost in Next Fiscal Year (Detail) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Pension Benefits [Member] | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Actuarial loss | $ (2.8) | $ (2.6) |
| Total | (2.8) | (2.6) |
| OPEB Benefits [Member] | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Prior service credit | 12.2 | 9.2 |
| Actuarial loss | (0.1) | (0.1) |
| Total | $ 12.1 | $ 9.1 |