XML 53 R41.htm IDEA: XBRL DOCUMENT v3.7.0.1
Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2016
Income Tax [Line Items]          
Net deferred income tax assets         $ 49.7
Effective rate tax adjustment related to federal tax, amount   $ 2.1   $ 2.1  
Decrease in effective tax rate   12.20%   8.60%  
Decrease in unrecognized tax positions $ 1.8   $ 1.8    
Interest and penalties     1.7    
ASU 2016-09 [Member]          
Income Tax [Line Items]          
Effective tax rate adjustment associated with stock compensation $ 1.5   $ 1.2    
Percentage of increase in effective tax rate associated with stock compensation 15.60%   5.90%