Pro Forma Consolidated Financial Information - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Business Acquisition Pro Forma Information [Abstract]
Pro forma acquisition related expenses	$ 0	$ 2,700,000

Asset acquisition proforma acquisition related costs.

No definition available.

Name:	ck0001698538_AssetAcquisitionProformaAcquisitionRelatedCosts
Namespace Prefix:	ck0001698538_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration