Other intangible assets (Details 2) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 31,515,000	$ 11,323,000	$ 31,515,000	$ 11,323,000	$ 15,246,000
Amortization of intangible assets	2,700,000	500,000	4,700,000	1,100,000
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	30,087,000	14,601,000	30,087,000	14,601,000	17,958,000
Intangible assets, less accumulated amortization	5,239,000	5,629,000	5,239,000	5,629,000	6,268,000
Intangible assets, net (excluding goodwill)	24,848,000	8,972,000	24,848,000	8,972,000	11,690,000
Noncompete agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	4,229,000	3,179,000	4,229,000	3,179,000	3,439,000
Intangible assets, less accumulated amortization	2,084,000	1,798,000	2,084,000	1,798,000	1,957,000
Intangible assets, net (excluding goodwill)	2,145,000	1,381,000	2,145,000	1,381,000	1,482,000
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	13,060,000	6,578,000	13,060,000	6,578,000	8,094,000
Intangible assets, less accumulated amortization	8,538,000	5,608,000	8,538,000	5,608,000	6,020,000
Intangible assets, net (excluding goodwill)	$ 4,522,000	$ 970,000	4,522,000	$ 970,000	$ 2,074,000
Series of individually immaterial business combinations
Finite-Lived Intangible Assets [Line Items]
Other intangible assets acquired			$ 21,000,000.0