10. Goodwill and Intangibles, net

Goodwill

The carrying amount of goodwill by segment were as follows (in millions):



	Construction			Marine Services		Energy		Telecom			Insurance		Broadcasting			Total
Balance at December 31, 2018		$	82.2	$	14.3	$	2.1	$	4.4		$	47.3		$	21.4	$	171.7
Measurement period adjustment		7.1		—		—		—			—			—		7.1
Impairments		—		—		—		(0.4		)	—			—		(0.4		)
Balance at June 30, 2019		$	89.3	$	14.3	$	2.1	$	4.0		$	47.3		$	21.4	$	178.4

Indefinite-lived Intangible Assets

Balances of indefinite-lived intangible assets as of June 30, 2019 and December 31, 2018 were as follows (in millions):



	June 30, 2019		December 31, 2018
FCC licenses	$	132.6	$	120.6
State licenses	2.5		2.5
Total	$	135.1	$	123.1

In 2019, FCC licenses increased $12.0 million, $12.9 million of which was through acquisitions, offset by $0.9 million of impairments.

Definite Lived Intangible Assets

The gross carrying amount and accumulated amortization of amortizable intangible assets by major intangible asset class is as follows (in millions):



	Weighted-Average Original Useful Life	June 30, 2019							December 31, 2018
	Weighted-Average Original Useful Life	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
Trade names	13 Years	$	26.0	$	(7.0	)	$	19.0	$	25.9	$	(5.9	)	$	20.0
Customer relationships	10 Years	53.6		(11.5		)	42.1		53.6		(7.2		)	46.4
Channel sharing arrangements	40 Years	25.2		(0.5		)	24.7		25.2		—			25.2
Developed technology	5 Years	1.2		(1.2		)	—		1.2		(1.2		)	—
Other	6 Years	5.5		(1.5		)	4.0		5.5		(1.0		)	4.5
Total		$	111.5	$	(21.7	)	$	89.8	$	111.4	$	(15.3	)	$	96.1

Amortization expense for definite lived intangible assets for the three months ended June 30, 2019 and 2018 was $3.1 million and $1.1 million, respectively, and was included in Depreciation and amortization in the Condensed Consolidated Statements of Operations.

Amortization expense for definite lived intangible assets for the six months ended June 30, 2019 and 2018 was $6.3 million and $2.1 million, respectively, and was included in Depreciation and amortization in the Condensed Consolidated Statements of Operations.

Excluding the impact of any future acquisitions, dispositions or change in foreign currency, the Company estimates the annual amortization expense of amortizable intangible assets for the next five fiscal years will be as follows (in millions):



Fiscal Year	Estimated Amortization Expense
2019	$	5.5
2020	$	8.1
2021	$	7.9
2022	$	7.7
2023	$	6.9