Goodwill and intangible assets - Company's other intangible assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 34,783	$ 34,783
Accumulated amortization	11,633	8,771
Net	$ 23,150	26,012
Licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization Period (in years)	10 years
Gross Carrying Amount	$ 1,000	1,000
Accumulated amortization	$ 1,000	1,000
Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization Period (in years)	5 years
Gross Carrying Amount	$ 386	386
Accumulated amortization	386	383
Net		3
Covenant not to compete [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,270	1,270
Accumulated amortization	937	783
Net	$ 333	487
Covenant not to compete [Member] | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period (in years)	10 years
Covenant not to compete [Member] | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period (in years)	6 years
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 31,560	31,560
Accumulated amortization	9,167	6,506
Net	$ 22,393	25,054
Customer relationships [Member] | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period (in years)	12 years
Customer relationships [Member] | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period (in years)	3 years
Above market leases [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization Period (in years)	13 years
Gross Carrying Amount	$ 567	567
Accumulated amortization	143	99
Net	$ 424	$ 468