Goodwill rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Goodwill [Roll Forward]
Balance at beginning of period	$ 765,386	$ 714,963	$ 714,963
Goodwill acquired during the year	0	0	50,640
Measurement period adjustments	(2,124)	0	(217)
Balance at end of period	763,262	714,963	765,386
Natural gas distribution
Goodwill [Roll Forward]
Balance at beginning of period	345,736	345,736	345,736
Goodwill acquired during the year	0	0	0
Measurement period adjustments	0	0	0
Balance at end of period	345,736	345,736	345,736
Construction materials and contracting
Goodwill [Roll Forward]
Balance at beginning of period	276,426	226,003	226,003
Goodwill acquired during the year	0	0	50,640
Measurement period adjustments	(2,124)	0	(217)
Balance at end of period	274,302	226,003	276,426
Construction services
Goodwill [Roll Forward]
Balance at beginning of period	143,224	143,224	143,224
Goodwill acquired during the year	0	0	0
Measurement period adjustments	0	0	0
Balance at end of period	$ 143,224	$ 143,224	$ 143,224