Basis of Presentation - Additional Information (Detail) - USD ($) $ in Millions |
Sep. 30, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Organization Consolidation And Presentation Of Financial Statements [Abstract] | ||
| Percentage inventory valued under LIFO | 99.00% | 98.00% |
| Higher inventory if FIFO applied entirely | $ 147.5 | $ 139.6 |