Estimated Fair Value of Outstanding Debt Balances (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ||
| Carrying value of Debt | $ 600,000 | $ 855,000 |
| Fair value of Debt | 546,728 | 793,441 |
| Term Loan Facility | ||
| Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ||
| Carrying value of Debt | 70,000 | |
| Fair value of Debt | 70,000 | |
| 2015 Term Loan | ||
| Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ||
| Carrying value of Debt | 185,000 | |
| Fair value of Debt | 185,000 | |
| 4.97% Series A Senior Notes, Due October 5th 2020 | ||
| Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ||
| Carrying value of Debt | 300,000 | 300,000 |
| Fair value of Debt | 283,534 | 279,635 |
| 4.27% Series B Senior Notes, Due June 14th 2022 | ||
| Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ||
| Carrying value of Debt | 300,000 | 300,000 |
| Fair value of Debt | $ 263,194 | $ 258,806 |