Net Income per Share - Additional Information (Detail)
|
3 Months Ended |
6 Months Ended |
|
Jun. 25, 2016
Employee
shares
|
Jun. 27, 2015
shares
|
Jun. 25, 2016
Employee
shares
|
Jun. 27, 2015
shares
|
| Earnings Per Share Disclosure [Line Items] |
|
|
|
|
| Stock options cancelled during the period |
|
|
30,514
|
|
| Investment Share Program |
|
|
|
|
| Earnings Per Share Disclosure [Line Items] |
|
|
|
|
| Requirement tenure of employee for investment share program, purchase shares at discount |
|
|
2 years
|
|
| Vesting period |
|
|
5 years
|
|
| Investment Share Program | Minimum |
|
|
|
|
| Earnings Per Share Disclosure [Line Items] |
|
|
|
|
| Requirement tenure of employee for investment share program |
|
|
1 year
|
|
| Discount from current market value |
|
|
20.00%
|
|
| Investment Share Program | Maximum |
|
|
|
|
| Earnings Per Share Disclosure [Line Items] |
|
|
|
|
| Discount from current market value |
|
|
40.00%
|
|
| Common Class A |
|
|
|
|
| Earnings Per Share Disclosure [Line Items] |
|
|
|
|
| Antidilutive securities excluded from computation of earnings per share |
737,000
|
6,000
|
695,000
|
5,000
|
| Common Class A | Performance-Based Awards |
|
|
|
|
| Earnings Per Share Disclosure [Line Items] |
|
|
|
|
| Number of shares not included because the performance criteria was not met as of the end of the reporting period |
|
|
36,000
|
37,000
|
| Stock options cancelled during the period |
|
|
14,742
|
|
| Common Class A | Performance-Based Awards | Key Employee |
|
|
|
|
| Earnings Per Share Disclosure [Line Items] |
|
|
|
|
| Options granted in period |
|
|
30,000
|
|
| Number of employees | Employee |
2
|
|
2
|
|
| Common Class A | Performance-Based Awards | Executive Officers |
|
|
|
|
| Earnings Per Share Disclosure [Line Items] |
|
|
|
|
| Options granted in period |
|
|
6,000
|
|
| Common Class A | Special long-term service-based retention stock option issued to the Chief Executive Officer |
|
|
|
|
| Earnings Per Share Disclosure [Line Items] |
|
|
|
|
| Stock options cancelled during the period |
|
|
15,772
|
|