Goodwill and intangible assets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 34,883	$ 34,883
Accumulated Amortization	6,906	5,432
Net	$ 27,977	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	467	417
Net	$ 533	583
Patents [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period (in years)	5 years
Gross Carrying Amount	$ 386	386
Accumulated Amortization	382	380
Net	4	6
Covenant not to compete [Member]
Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	1,270	1,270
Accumulated Amortization	706	629
Net	$ 564	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	$ 31,660	31,660
Accumulated Amortization	5,275	3,952
Net	$ 26,385	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)	10 years
Above market leases [Member]
Indefinite-lived Intangible Assets [Line Items]
Amortization Period (in years)	13 years
Gross Carrying Amount	$ 567	567
Accumulated Amortization	76	54
Net	$ 491	$ 513