Income taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Investment in flow-through entity	$ 15,537	$ 1,958
Net deferred tax asset	$ 15,537	$ 1,958

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from the entity's investment in its wholly-owned subsidiaries.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 25
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=117330534&loc=d3e28680-109314

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319

Name:	us-gaap_DeferredTaxAssetsInvestmentInSubsidiaries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant