Receivables and allowance for expected credit losses (Details 2) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses							$ 3,258	$ (801)
Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	$ 9,565	$ 10,156	$ 9,716	$ 10,748	$ 12,714	$ 15,358	9,716	15,358
Provision for credit losses	1,015	509	1,735	357	(841)	(317)
Less write-offs charged against the allowance	2,448	1,385	1,627	2,152	1,424	2,669
Credit loss recoveries collected	294	285	332	353	299	342
Balance	8,426	9,565	10,156	9,306	10,748	12,714	8,426	9,306
Electric | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	348	361	269	327	678	899	269	899
Provision for credit losses	300	113	565	388	(110)	538
Less write-offs charged against the allowance	399	234	597	525	341	888
Credit loss recoveries collected	85	108	124	92	100	129
Balance	334	348	361	282	327	678	334	282
Natural gas distribution | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	1,453	2,123	1,506	2,259	2,950	2,571	1,506	2,571
Provision for credit losses	881	92	1,369	411	(103)	1,273
Less write-offs charged against the allowance	1,822	939	932	1,178	787	1,107
Credit loss recoveries collected	169	177	180	168	199	213
Balance	681	1,453	2,123	1,660	2,259	2,950	681	1,660
Pipeline | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2	2	2	2	2	2	2	2
Provision for credit losses	0	0	0	0	0	0
Less write-offs charged against the allowance	0	0	0	0	0	0
Credit loss recoveries collected	0	0	0	0	0	0
Balance	2	2	2	2	2	2	2	2
Construction materials and contracting | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	5,030	5,126	5,406	4,621	4,842	6,164	5,406	6,164
Provision for credit losses	(55)	12	(253)	233	11	(1,049)
Less write-offs charged against the allowance	75	108	27	184	232	273
Credit loss recoveries collected	0	0	0	0	0	0
Balance	4,900	5,030	5,126	4,670	4,621	4,842	4,900	4,670
Construction services | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2,732	2,544	2,533	3,539	4,242	5,722	2,533	5,722
Provision for credit losses	(111)	292	54	(675)	(639)	(1,079)
Less write-offs charged against the allowance	152	104	71	265	64	401
Credit loss recoveries collected	40	0	28	93	0	0
Balance	$ 2,509	$ 2,732	$ 2,544	$ 2,692	$ 3,539	$ 4,242	$ 2,509	$ 2,692