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Significant Accounting Policies - 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
Accounting Policies [Abstract]          
Accounts receivable $ 21.5   $ 21.5   $ 10.3
Advertising expenses $ 0.8 $ 0.8 $ 1.6 $ 1.4