Goodwill and intangible assets - Company's other intangible assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 33,397	$ 33,397
Accumulated amortization	12,342	10,247
Net	21,055	23,150
Covenant not to compete [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,270	1,270
Accumulated amortization	1,002	937
Net	$ 268	333
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	11,163	9,167
Net	$ 20,397	22,393
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)	10 years
Above market leases [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization Period (in years)	13 years
Gross Carrying Amount	$ 567	567
Accumulated amortization	177	143
Net	$ 390	$ 424