Gross Carrying and Fair Value of Senior Notes (Detail) - USD ($) $ in Thousands |
Jun. 30, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Debt Instrument [Line Items] | ||
| Carrying value | $ 245,531 | $ 245,212 |
| Senior Notes 5.875 Percent Due 2024 | ||
| Debt Instrument [Line Items] | ||
| Carrying value | 250,000 | 250,000 |
| Fair value | $ 261,250 | $ 258,750 |