Computation of Diluted Net Income Per Share (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands |
3 Months Ended |
Mar. 26, 2016 |
Mar. 28, 2015 |
| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] |
|
|
| Allocation of net income for basic common stock |
$ 7,032
|
$ 13,743
|
| Weighted-average number of common shares - diluted |
13,088
|
13,633
|
| Net income per common share - basic |
$ 0.55
|
$ 1.04
|
| Net income per common share - diluted |
$ 0.53
|
$ 1.00
|
| Common Class A |
|
|
| Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items] |
|
|
| Allocation of net income for basic common stock |
$ 5,149
|
$ 9,934
|
| Allocation of net income to Class B Common Stock |
1,849
|
3,744
|
| Net effect of unvested participating shares |
1
|
2
|
| Net Income for diluted common stock |
$ 6,999
|
$ 13,680
|
| Weighted-average number of common shares - basic |
9,375
|
9,598
|
| Add: effect of dilutive potential common share-based awards |
346
|
418
|
| Weighted average number of shares of Class B Common Stock |
3,367
|
3,617
|
| Weighted-average number of common shares - diluted |
13,088
|
13,633
|
| Net income per common share - basic |
$ 0.55
|
$ 1.04
|
| Net income per common share - diluted |
$ 0.53
|
$ 1.00
|