Related Party Transactions - Additional Information (Detail) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
	May 03, 2019	Sep. 30, 2019	Dec. 31, 2018
Spectrum Inc.
Related Party Transaction [Line Items]
Spectrum Acquisition, tax preparation and other fees		$ 0.4	$ 0.2
Principal Owner
Related Party Transaction [Line Items]
Accrued refunds current			$ 1.7
Principal Owner | Spectrum Inc. | IPO [Member]
Related Party Transaction [Line Items]
Outstanding common stock until the company completed its public offering	3,144,531
Principal Owner | Minimum | Spectrum Inc. | IPO [Member]
Related Party Transaction [Line Items]
Non controlling ownership interest minimum	10.00%