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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Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Intangible Assets, by category
Gross Carrying Amount	$ 524,216		$ 524,216		$ 523,048
Accumulated Amortization	101,310		101,310		84,483
Amortization expense for intangible assets	8,183	$ 8,352	16,399	$ 14,270
Estimated amortization expense for next 5 years
2021	32,900		32,900
2022	32,400		32,400
2023	32,300		32,300
2024	31,800		31,800
2025	31,600		31,600
Customer related
Intangible Assets, by category
Gross Carrying Amount	109,846		109,846		109,378
Accumulated Amortization	52,732		52,732		48,057
Permits and rights
Intangible Assets, by category
Gross Carrying Amount	308,843		308,843		308,705
Accumulated Amortization	26,889		26,889		18,955
Patents
Intangible Assets, by category
Gross Carrying Amount	202		202		192
Accumulated Amortization	151		151		139
Technology related
Intangible Assets, by category
Gross Carrying Amount	40,763		40,763		40,274
Accumulated Amortization	11,742		11,742		9,654
Trade Names [Member]
Intangible Assets, by category
Gross Carrying Amount	32,004		32,004		31,949
Accumulated Amortization	6,167		6,167		4,834
Air Rights [Member]
Intangible Assets, by category
Gross Carrying Amount	26,139		26,139		26,139
Accumulated Amortization	1,414		1,414		1,044
Other
Intangible Assets, by category
Gross Carrying Amount	3,919		3,919		3,911
Accumulated Amortization	1,434		1,434		1,331
Non-compete agreement
Intangible Assets, by category
Gross Carrying Amount	2,500		2,500		2,500
Accumulated Amortization	$ 781		$ 781		$ 469