Revenue (Tables)

9 Months Ended

Sep. 30, 2019

Revenue from Contract with Customer [Abstract]

Schedule of remaining performance obligation

The Company expects to recognize the remaining performance obligations as revenue in future periods as follows:

(millions) (unaudited)	Remaining Performance Obligations
2019	$	17.9
2020	50.2
2021	29.9
2022	14.6
2023	10.3
2024 and thereafter	12.4
Total	$	135.3

Schedule of contract with customer, asset and liability

The following table provides information about accounts receivable, contract assets and contract liabilities with customers and clients as of September 30, 2019 (unaudited) and December 31, 2018:

(millions)	September 30, 2019			December 31, 2018
Accounts receivable	$	139.7		$	139.3
Contract asset	$	10.3		$	11.4
Contract liability	$	(16.3	)	$	(19.1	)

The following table provides information about changes to contract asset balances for the nine-month periods ended September 30, 2019 and 2018:

	Nine Months Ended
(millions) (unaudited)	September 30, 2019			September 30, 2018
Balance, beginning of period	$	11.4		$	12.2
Additional contract assets	96.4			100.0
Reclassification to accounts receivable	(97.5		)	(101.4		)
Balance, end of period	$	10.3		$	10.8

The following table provides information about changes to contract liability balances for the nine-month periods ended September 30, 2019 and 2018:

	Nine Months Ended
(millions) (unaudited)	September 30, 2019			September 30, 2018
Balance, beginning of period	$	19.1		$	20.5
Additional contract liabilities	122.2			128.6
Recognition of revenue from contract liabilities	(125.0		)	(132.6		)
Balance, end of period	$	16.3		$	16.5

Schedule of amortization expense related to cost of contracts

The table below shows amortization expense related to cost of contracts for the three and nine months ended September 30, 2019 and 2018. Amortization expense of cost of contracts related to service concession arrangements within the scope of Topic 853 and certain management type contracts are recorded as a reduction of revenue and were not significant for the three and nine months ended September 30, 2019 and 2018, respectively.

	Three Months Ended				Nine Months Ended
(millions) (unaudited)	September 30, 2019		September 30, 2018		September 30, 2019		September 30, 2018
Amortization expense related to cost of contract included in depreciation and amortization	$	0.3	$	0.8	$	0.9	$	2.3