Computer Software

12 Months Ended

Dec. 31, 2018

Research and Development [Abstract]

Computer Software

Computer Software

Computer software, net consists of the following (in millions):

	December 31,
	2018			2017
Internally developed software	$	746.0		$	679.4
Purchased software	60.7			45.7
Computer software	806.7			725.1
Accumulated amortization	(401.1		)	(308.3		)
Computer software, net	$	405.6		$	416.8

Internally developed software and purchased software are inclusive of amounts acquired through acquisitions.

Estimated amortization expense on computer software for the next five fiscal years is as follows (in millions):

2019 (1)	$	93.6
2020	92.5
2021	77.8
2022	68.0
2023	59.4

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(1) Assumes assets not in service as of December 31, 2018 are placed in service equally throughout the year.