Long Term Debt - Components of Long-term Debt (Detail) - USD ($) $ in Thousands |
Dec. 31, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Debt Instrument [Line Items] | ||
| Long-term debt | $ 557,500 | $ 543,000 |
| 5.25% Senior Notes due March 15, 2019 [Member] | ||
| Debt Instrument [Line Items] | ||
| Long-term debt | 500,000 | 500,000 |
| 5.25% Senior Notes due March 15, 2019 [Member] | Senior Notes [Member] | ||
| Debt Instrument [Line Items] | ||
| Long-term debt | 500,000 | 500,000 |
| Revolving Credit Facility [Member] | ||
| Debt Instrument [Line Items] | ||
| Long-term debt | $ 57,500 | $ 43,000 |