Share-Based Compensation - Activity in Company's Plan (Detail) - 1999 Stock Option Plan [Member]
$ / shares in Units, $ in Thousands |
12 Months Ended |
|
Dec. 31, 2016
USD ($)
$ / shares
shares
|
|---|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
| Outstanding at January 1, 2016, Number of Shares | shares |
12,000
|
| Exercised, Number of Shares | shares |
(6,450)
|
| Forfeited, Number of Shares | shares |
0
|
| Outstanding (exercisable and vested) at December 31, 2016, Number of Shares | shares |
5,550
|
| Outstanding at January 1, 2016, Weighted Average Exercise Price per Share | $ / shares |
$ 41.44
|
| Exercised, Weighted Average Exercise Price per Share | $ / shares |
35.50
|
| Forfeited, Weighted Average Exercise Price per Share | $ / shares |
0.00
|
| Outstanding (exercisable and vested) at December 31, 2016, Weighted Average Exercise Price per Share | $ / shares |
$ 48.35
|
| Outstanding (exercisable and vested), Weighted Average Remaining Contractual Term |
1 year 9 months 18 days
|
| Outstanding (exercisable and vested) Aggregate Intrinsic Value | $ |
$ 54
|