Income Taxes - Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Income Tax Disclosure [Abstract] | ||
| Beginning Balance | $ 6.3 | $ 6.4 |
| Change in balances related to tax positions | 0.0 | (0.1) |
| Ending Balance | $ 6.3 | $ 6.3 |