Cost of Contracts, net (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Schedule of contract cost

The table below shows the Company's amortization expense related to costs of contracts for the years ended December 31, 2018, 2017 and 2016, and is primarily included in Depreciation and amortization within the Consolidated Statements of Income.

	Year Ended December 31,
(millions)	2018		2017		2016
Amortization expense	$	3.0	$	3.2	$	3.4
Weighted average life (years)	9.4		9.8		9.6

The expected future amortization of cost of contracts is as follows:

(millions)	Cost of Contract
2019	$	2.8
2020	1.7
2021	1.2
2022	1.1
2023	0.8
2024 and Thereafter	1.6
Total	$	9.2

Cost of contracts, net, is comprised of the following:

	December 31,
(millions)	2018			2017
Cost of contracts	$	33.8		$	30.5
Accumulated amortization	(24.6		)	(21.6		)
Cost of contracts, net	$	9.2		$	8.9