XML 73 R59.htm IDEA: XBRL DOCUMENT v3.7.0.1
Employee Deferred Compensation Plan and Employee Stock Purchase Plan - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 12 Months Ended
Jun. 30, 2001
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Jun. 30, 2011
Employee Stock Ownership Plan E S O P Disclosures [Line Items]          
Percentage contribution, compensation   100.00%      
Matching percentage, employee contribution   5.00%      
Company's contributions amount   $ 1,258 $ 1,261 $ 1,445  
Common stock under employee stock purchase plan, par value   $ 0.10 $ 0.10    
Shares of common stock purchased through the plan   42,730 50,452 47,213  
Employee Stock Purchase Plan          
Employee Stock Ownership Plan E S O P Disclosures [Line Items]          
Number of common stock shares under employee stock purchase plan 1,000,000        
Common stock under employee stock purchase plan, par value $ 0.10        
Employee stock purchase plan offering period   January 1 and July 1 of each year      
Employee stock purchase plan expiration date   Dec. 31, 2018      
Commons stock plan available for sale under plan         995,000
Available common stock under plan   760,825 803,555 854,007