Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Description of the Business and Summary of Significant Accounting Policies - Narrative (Details) $ in Millions		3 Months Ended
	May 07, 2019	Mar. 31, 2020 segment	Mar. 31, 2019 USD ($)
Subsidiary, Sale of Stock [Line Items]
Economic interests called by common stock units	18.00%
Number of operating segments \| segment		1
Revenue recognized \| $			$ 0.4
IPO \| Class A common stock
Subsidiary, Sale of Stock [Line Items]
Economic interests called by common stock units	100.00%
SG Holding I
Subsidiary, Sale of Stock [Line Items]
Economic interests called by common stock units	82.00%