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Revenue - Deferred Revenue (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Revenue from Contract with Customer [Abstract]          
Deferred revenue $ 1,766,464   $ 1,766,464   $ 1,868,223
Losses on receivables $ 45,646 $ 188,383 $ 358,396 $ 414,114