Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Intangible Assets, by category
Gross Carrying Amount	$ 523,318		$ 523,048
Accumulated Amortization	92,729		84,483
Amortization expense for intangible assets	8,216	$ 5,918
Estimated amortization expense for next 5 years
2021	32,900
2022	32,400
2023	32,300
2024	31,800
2025	31,600
Customer related
Intangible Assets, by category
Gross Carrying Amount	109,413		109,378
Accumulated Amortization	50,272		48,057
Permits and rights
Intangible Assets, by category
Gross Carrying Amount	308,779		308,705
Accumulated Amortization	22,923		18,955
Patents
Intangible Assets, by category
Gross Carrying Amount	173		192
Accumulated Amortization	127		139
Technology related
Intangible Assets, by category
Gross Carrying Amount	40,492		40,274
Accumulated Amortization	10,684		9,654
Trade Names [Member]
Intangible Assets, by category
Gross Carrying Amount	31,973		31,949
Accumulated Amortization	5,500		4,834
Air Rights [Member]
Intangible Assets, by category
Gross Carrying Amount	26,139		26,139
Accumulated Amortization	1,239		1,044
Other
Intangible Assets, by category
Gross Carrying Amount	3,849		3,911
Accumulated Amortization	1,359		1,331
Non-compete agreement
Intangible Assets, by category
Gross Carrying Amount	2,500		2,500
Accumulated Amortization	$ 625		$ 469

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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