Goodwill and intangible assets - Company's other intangible assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 34,783	$ 34,883
Accumulated Amortization	8,771	5,432
Net	$ 26,012	29,451
Licenses [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period (in years)	10 years
Gross Carrying Amount	$ 1,000	1,000
Accumulated Amortization	$ 1,000	417
Net		583
Patents [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period (in years)	5 years
Gross Carrying Amount	$ 386	386
Accumulated Amortization	383	380
Net	3	6
Covenant not to compete [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	1,270	1,270
Accumulated Amortization	783	629
Net	$ 487	641
Covenant not to compete [Member] | Maximum
Indefinite-lived Intangible Assets [Line Items]
Amortization Period (in years)	10 years
Covenant not to compete [Member] | Minimum
Indefinite-lived Intangible Assets [Line Items]
Amortization Period (in years)	6 years
Customer relationships [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 31,560	31,660
Accumulated Amortization	6,506	3,952
Net	$ 25,054	27,708
Customer relationships [Member] | Maximum
Indefinite-lived Intangible Assets [Line Items]
Amortization Period (in years)	12 years
Customer relationships [Member] | Minimum
Indefinite-lived Intangible Assets [Line Items]
Amortization Period (in years)	3 years
Above market leases [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period (in years)	13 years
Gross Carrying Amount	$ 567	567
Accumulated Amortization	99	54
Net	$ 468	$ 513