Intangible Assets and Goodwill

12 Months Ended

Dec. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets and Goodwill

8. Intangible Assets and Goodwill

The following tables present certain information regarding our intangible assets. Amortizable intangible assets are being amortized on a straight-line basis over their estimated useful lives of ten years with no estimated residual values, which materially approximates the expected pattern of use.

	December 31, 2019			September 30, 2018
	(in millions)
Trademarks	$	21.6		$	17.6
Customer relationships		20.1			15.1
		41.7			32.7
Less: accumulated amortization		(31.8	)		(27.0	)
	$	9.9		$	5.7

Aggregate intangible asset amortization expense amounted to $3.5 million, $0.8 million and $3.4 million for the year ended December 31, 2019, the three months ended December 31, 2018 and the year ended September 30, 2018, respectively.

The estimated intangible asset amortization expense for the years ending December 31 are as follows:

Year ending December 31, (in millions)
2020	$	2.4
2021		0.8
2022		0.8
2023		0.8
2024		0.8
Thereafter		4.3
Total	$	9.9

Goodwill

Goodwill is summarized as follows:

	December 31, 2019		September 30, 2018
	(in millions)
Balance at beginning of period	$	44.9	$	47.1
Foreign currency translation adjustments		3.9		(1.3	)
Acquisition of NTG		32.1		—
Ending balance	$	80.9	$	45.8