Other Intangible Assets

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Other Intangible Assets

Other Intangible Assets

	December 31, 2017							December 31, 2016
	Weighted Average Useful Life (Years)	Gross Value		Accumulated Amortization		Net Value		Gross Value		Accumulated Amortization		Net Value
		(In millions)
Customer relationships	9.2	$	83.4	$	29.3	$	54.1	$	75.5	$	23.7	$	51.8
Indefinite-lived tradenames	*	23.7		*		23.7		22.4		*		22.4
Technology	17.5	23.6		3.0		20.6		23.0		1.8		21.2
Other	7.2	4.1		3.0		1.1		4.0		2.8		1.2
Total		$	134.8	$	35.3	$	99.5	$	124.9	$	28.3	$	96.6
* Not applicable, as these tradenames have an indefinite life.

As part of HAT acquisition, we acquired approximately $2.0 million of customer relationships. As described in Note 3, the fair value of this intangible asset is subject to finalization of its fair value analysis, expected to be completed not later than twelve months after the acquisition date.

As part of the GH acquisition, we acquired approximately $3.6 million of customer relationships, $4.8 million of tradenames and $6.5 million of technology.

Amortization expense of other intangible assets follows:

	Year Ended December 31,
	2017		2016		2015
	(In millions)
Amortization expense	$	6.6	$	6.1	$	6.4

We estimate amortization expense for the five years subsequent to December 31, 2017 as follows:

	(In millions)
2018	$	6.8
2019	$	6.4
2020	$	6.2
2021	$	6.2
2022	$	6.2