Goodwill and other intangible assets (Tables)

12 Months Ended

Dec. 31, 2012

Goodwill [Line Items]

Changes in the carrying amount of goodwill

The changes in the carrying amount of goodwill for the year ended December 31, 2012, were as follows:

	Balance as of January 1, 2012		*	Goodwill Acquired During the Year		**	Balance as of December 31, 2012		*
	(In thousands)
Natural gas distribution	$	345,736		$	—		$	345,736
Pipeline and energy services	9,737			—			9,737
Construction materials and contracting	176,290			—			176,290
Construction services	103,168			1,108			104,276
Total	$	634,931		$	1,108		$	636,039

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

** Includes contingent consideration that was not material related to an acquisition in a prior period.

The changes in the carrying amount of goodwill for the year ended December 31, 2011, were as follows:

	Balance as of January 1, 2011		*	Goodwill Acquired During the Year		**	Balance as of December 31, 2011		*
	(In thousands)
Natural gas distribution	$	345,736		$	—		$	345,736
Pipeline and energy services	9,737			—			9,737
Construction materials and contracting	176,290			—			176,290
Construction services	102,870			298			103,168
Total	$	634,633		$	298		$	634,931

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

** Includes contingent consideration that was not material related to an acquisition in a prior period.

Other amortizable intangible assets

Other amortizable intangible assets at December 31 were as follows:

	2012			2011
	(In thousands)
Customer relationships	$	21,310		$	21,702
Accumulated amortization	(11,701		)	(10,392		)
	9,609			11,310
Noncompete agreements	7,236			7,685
Accumulated amortization	(5,326		)	(5,371		)
	1,910			2,314
Other	10,979			11,442
Accumulated amortization	(5,369		)	(4,223		)
	5,610			7,219
Total	$	17,129		$	20,843