Goodwill and other intangible assets

12 Months Ended

Dec. 31, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Other Intangible Assets

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 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

The previous tables include goodwill and intangible assets associated with the business combinations completed during 2021 and 2020. For more information related to these business combinations, see Note 4.

Amortization expense for amortizable intangible assets for the years ended December 31, 2021, 2020 and 2019, was $5.1 million, $9.0 million and $2.4 million, respectively. 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