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Stockholders' equity - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Accumulated Other Comprehensive Income Loss [Line Items]      
Number of shares authorized for repurchase     2,000,000
Shares available for repurchase under the plan 1,563,519 1,686,008  
Aggregate purchase price $ 1.0    
Treasury stock      
Accumulated Other Comprehensive Income Loss [Line Items]      
Stock repurchased and acquired in market transactions 122,489    
Aggregate purchase price $ 1.0