XML 18 R39.htm IDEA: XBRL DOCUMENT v3.19.3
Earnings Per Common Share - Additional Information (Detail) - shares
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Schedule Of Antidilutive Securities Included In Computation Of Earnings Per Share [Line Items]        
Shares contingently issuable under shareholder return plan     0 45,840
Stock Option [Member]        
Schedule Of Antidilutive Securities Included In Computation Of Earnings Per Share [Line Items]        
Securities excluded from computation of net income per diluted shares 352,250 0 352,250 117,600
Restricted Stock [Member]        
Schedule Of Antidilutive Securities Included In Computation Of Earnings Per Share [Line Items]        
Shares contingently issuable under shareholder return plan     30,137 17,081