Intangible Assets

Direct internal and external costs to develop software used by Technologies' customers are capitalized. Capitalized costs are amortized over the 6-year estimated useful life of the software, beginning when the software is complete and ready for sale. At September 30, 2017, the remaining weighted-average amortization period for external-use software was 3.7 years. Amortization expense related to such software assets was $2.4 million, $1.9 million and $1.6 million for 2017, 2016 and 2015, respectively. Amortization expense for each of the next five years is scheduled to be $3.9 million in 2018, $3.6 million in 2019, $3.3 million in 2020, $2.6 million in 2021 and $2.1 million in 2022.

At September 30, 2017, the remaining weighted-average amortization period for the business combination-related finite-lived intangible assets was 6.8 years. Amortization expense related to these assets was $19.7 million, $19.3 million and $24.3 million for 2017, 2016 and 2015, respectively. Amortization expense for each of the next five years is scheduled to be $20.0 million in 2018, $19.8 million in 2019, $19.8 million in 2020, $19.8 million in 2021 and $19.7 million in 2022.

Intangible assets are presented below.



	September 30,
	2017			2016
	(in millions)
Capitalized external-use software:
Cost	$	28.4		$	20.9
Accumulated amortization	(11.3		)	(8.9		)
Net book value	17.1			12.0

Business combination-related:
Cost:
Finite-lived intangible assets:
Technology	76.7			76.8
Customer relationships and other	359.2			350.5
Indefinite-lived intangible assets:
Trade names and trademarks	266.8			263.6
Goodwill	12.9			5.4
	715.6			696.3
Accumulated amortization:
Technology	(72.2		)	(71.5		)
Customer relationships and other	(221.2		)	(202.2		)
	(293.4		)	(273.7		)
Net book value	422.2			422.6
Total intangible assets net book value	$	439.3		$	434.6