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Income Taxes - Additional Information (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Income Tax Examination [Line Items]          
Corporate income tax rate     21.00%   35.00%
Provisional income tax expense         $ 3,300
Income tax benefit $ 1,765 $ 1,698 $ 5,575 $ 2,642  
Gross liability for tax positions 3,700   3,700    
Change in unrecognized tax benefits reasonably possible 3,000   $ 3,000    
Income tax examination years description     The Company is no longer subject to U.S. Federal income tax examinations for the years prior to 2014.    
Interest and Penalties          
Income Tax Examination [Line Items]          
Gross liability for tax positions $ 1,100   $ 1,100    
State Jurisdiction | Minimum          
Income Tax Examination [Line Items]          
Income tax examination year     2013    
State Jurisdiction | Maximum          
Income Tax Examination [Line Items]          
Income tax examination year     2017    
Domestic          
Income Tax Examination [Line Items]          
Effective income tax rate 22.10% 39.90% 22.10% 39.90%  
Foreign          
Income Tax Examination [Line Items]          
Effective income tax rate, change in enacted rate 23.80% 37.40% 23.80% 37.40%