Receivables and allowance for expected credit losses (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Provision for credit losses	$ 1,735	$ (317)
Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	9,716	15,358
Provision for credit losses	1,735	(317)
Less write-offs charged against the allowance	1,627	2,669
Credit loss recoveries collected	332	342
Balance	10,156	12,714
Electric | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	269	899
Provision for credit losses	565	538
Less write-offs charged against the allowance	597	888
Credit loss recoveries collected	124	129
Balance	361	678
Natural gas distribution | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	1,506	2,571
Provision for credit losses	1,369	1,273
Less write-offs charged against the allowance	932	1,107
Credit loss recoveries collected	180	213
Balance	2,123	2,950
Pipeline | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2	2
Provision for credit losses	0	0
Less write-offs charged against the allowance	0	0
Credit loss recoveries collected	0	0
Balance	2	2
Construction materials and contracting | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	5,406	6,164
Provision for credit losses	(253)	(1,049)
Less write-offs charged against the allowance	27	273
Credit loss recoveries collected	0	0
Balance	5,126	4,842
Construction services | Trade Accounts Receivable
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance	2,533	5,722
Provision for credit losses	54	(1,079)
Less write-offs charged against the allowance	71	401
Credit loss recoveries collected	28	0
Balance	$ 2,544	$ 4,242