Goodwill and other intangible assets (Tables)

12 Months Ended

Dec. 31, 2015

Goodwill and Intangible Assets Disclosure [Abstract]

Changes in the carrying amount of goodwill

The changes in the carrying amount of goodwill for the year ended December 31, 2015, were as follows:

	Balance at January 1, 2015		*	Goodwill Acquired During the Year		Balance at December 31, 2015		*
	(In thousands)
Natural gas distribution	$	345,736		$	—	$	345,736
Pipeline and midstream	9,737			—		9,737
Construction materials and contracting	176,290			—		176,290
Construction services	103,441			—		103,441
Total	$	635,204		$	—	$	635,204

* Balance is presented net of accumulated impairment of $12.3 million at the pipeline and midstream segment, which occurred in prior periods.

The changes in the carrying amount of goodwill for the year ended December 31, 2014, were as follows:

	Balance at January 1, 2014		*	Goodwill Acquired During the Year/Other			Balance at December 31, 2014		*
	(In thousands)
Natural gas distribution	$	345,736		$	—		$	345,736
Pipeline and midstream	9,737			—			9,737
Construction materials and contracting	176,290			—			176,290
Construction services	104,276			(835		)	103,441
Total	$	636,039		$	(835	)	$	635,204

* Balance is presented net of accumulated impairment of $12.3 million at the pipeline and midstream segment, which occurred in prior periods.

Other amortizable intangible assets

Other amortizable intangible assets at December 31 were as follows:

	2015			2014
	(In thousands)
Customer relationships	$	20,975		$	21,310
Accumulated amortization	(16,845		)	(15,556		)
	4,130			5,754
Noncompete agreements	4,409			5,080
Accumulated amortization	(3,655		)	(4,098		)
	754			982
Other	8,304			10,921
Accumulated amortization	(5,846		)	(7,817		)
	2,458			3,104
Total	$	7,342		$	9,840