Goodwill and other intangible assets (Tables)

12 Months Ended

Dec. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Changes in the carrying amount of goodwill

The changes in the carrying amount of goodwill were as follows:

	Balance at January 1, 2021		Goodwill Acquired During  the Year		Measurement Period Adjustments		Balance at December 31, 2021
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	—	$	345,736
Construction materials and contracting	226,003		50,640		(217)		276,426
Construction services	143,224		—		—		143,224
Total	$	714,963	$	50,640	$	(217)	$	765,386

	Balance at January 1, 2020		Goodwill Acquired During the Year		Measurement Period Adjustments		Balance at December 31, 2020
	(In thousands)
Natural gas distribution	$	345,736	$	—	$	—	$	345,736
Construction materials and contracting	217,234		8,778		(9)		226,003
Construction services	118,388		24,436		400		143,224
Total	$	681,358	$	33,214	$	391	$	714,963

Other amortizable intangible assets

Other amortizable intangible assets at December 31 were as follows:

	2021		2020
	(In thousands)
Customer relationships	$	29,740	$	28,836
Less accumulated amortization	10,650		6,887
	19,090		21,949
Noncompete agreements	4,591		3,941
Less accumulated amortization	2,856		2,309
	1,735		1,632
Other	12,601		12,927
Less accumulated amortization	10,848		11,012
	1,753		1,915
Total	$	22,578	$	25,496

Estimated amortization expense

The amounts of estimated amortization expense for identifiable intangible assets as of December 31, 2021, were:

	2022		2023		2024		2025		2026		Thereafter
	(In thousands)
Amortization expense	$	4,928	$	4,578	$	4,308	$	2,314	$	1,693	$	4,757