Intangible Assets, net

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets, net

9. Intangible Assets, net

Intangible assets include customer relationships and contracts associated with various business and asset acquisitions. These acquired intangible assets were recorded at fair value determined as of the acquisition date and are being amortized over the period we expect to benefit from the assets. Intangible assets, net consisted of the following (in thousands):

	December 31, 2019					December 31, 2018
	Gross  Carrying  Amount		Accumulated Amortization			Gross  Carrying  Amount		Accumulated Amortization
Customer-related (10-25 year life)	$	147,244	$	(76,176	)	$	107,008	$	(69,678	)
Contract-based (5-7 year life)	37,773		(31,370		)	64,556		(49,516		)
Intangible assets	$	185,017	$	(107,546	)	$	171,564	$	(119,194	)

Amortization expense of these intangible assets totaled $15.3 million, $16.5 million and $17.8 million during the years ended December 31, 2019, 2018 and 2017, respectively.

Estimated future intangible assets amortization expense is as follows (in thousands):

2020	$	15,675
2021	11,416
2022	9,078
2023	7,225
2024	6,136
Thereafter	27,941
Total	$	77,471