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Accounting Policies - Additional Information (Detail)
3 Months Ended
Nov. 14, 2016
Oct. 18, 2016
$ / shares
Mar. 31, 2017
USD ($)
$ / shares
shares
Mar. 31, 2016
shares
Dec. 31, 2016
$ / shares
Regulatory Assets [Abstract]          
Stock split ratio 1.5 1.5      
Common stock, par value | $ / shares   $ 0  
Shares, non-dilutive | shares     0 0  
Reclassifications effect on net income | $     $ 0