Goodwill and Other Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2018

Goodwill And Intangible Assets Disclosure [Abstract]

Changes in Goodwill

	Mid-America		Southeast			West
	Group		Group			Group		Total
	(Dollars in Thousands)
Balance at January 1, 2018	$	281,403	$	50,346		$	1,828,541	$	2,160,290
Acquisitions		148,326		93,816			—		242,142
Divestitures		—		(927	)		—		(927	)
Balance at June 30, 2018	$	429,729	$	143,235		$	1,828,541	$	2,401,505

Intangible Assets Subject to Amortization

Intangible assets subject to amortization consist of the following:

	Gross Amount		Accumulated Amortization			Net Balance
(Dollars in Thousands)	June 30, 2018
Noncompetition agreements	$	6,274	$	(6,162	)	$	112
Customer relationships		65,348		(19,480	)		45,868
Operating permits		458,952		(29,790	)		429,162
Use rights and other		16,496		(10,763	)		5,733
Trade names		12,800		(9,076	)		3,724
Total	$	559,870	$	(75,271	)	$	484,599

Intangible Assets Deemed to Indefinite Life and Not Being Amortized

Intangible assets deemed to have an indefinite life and not being amortized consist of the following:

	Building Materials Business		Magnesia Specialties		Total
(Dollars in Thousands)	June 30, 2018
Operating permits	$	6,600	$	—	$	6,600
Use rights		20,642		—		20,642
Trade names		280		2,565		2,845
Total	$	27,522	$	2,565	$	30,087

Schedule of Acquired Intangibles

Intangibles acquired during the year are as follows:

(Dollars in Thousands)	Amount		Weighted-average amortization period
Subject to amortization:
Customer relationships	$	20,620	12 years
Not subject to amortization:
Water rights		1,100	N/A
Total	$	21,720

Estimated Amortization Expense of Intangible Assets

The estimated amortization expense for intangible assets for the second half of 2018 and for each of the next four years and thereafter is as follows:

(Dollars in Thousands)
July - December 2018	$	6,961
2019		13,724
2020		13,689
2021		12,998
2022		11,490
Thereafter		425,737
Total	$	484,599