Revenue from Contracts with Customers (Tables)

9 Months Ended

Sep. 30, 2018

Revenue from Contract with Customer [Abstract]

Contract with Customer, Asset and Liability [Table Text Block]

The following table summarizes our trade receivables, contract assets and contract liabilities (in millions):



	September 30, 2018		December 31, 2017
Current contract assets	$	3.0	$	3.0
Noncurrent contract assets	$	—	$	2.8
Current contract liabilities (deferred revenue)	$	69.0	$	71.9
Noncurrent contract liabilities (deferred revenue)	$	13.4	$	51.2

Significant changes in contract assets and liabilities during the period are as follows (in millions):



	Contract Assets			Contract Liabilities
Balance as of December 31, 2017	$	5.8		$	123.1
Increase due to cash received	—			32.0
Decrease due to amortization of deferred revenue that was included in the beginning contract liability balance	—			(57.6		)
Decrease due to amortization of deferred revenue that was added during the period	—			(15.1		)
Decrease due to transfer to receivables during the period	(2.8		)	—
Balance as of September 30, 2018	$	3.0		$	82.4

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]

Expected future amortization of our contract liabilities and deferred costs recorded as of September 30, 2018 is set forth in the table below (in millions):



	Remaining 2018		2019		2020		2021 and Thereafter		Total
Amortization of contract liabilities	$	23.3	$	48.5	$	6.4	$	4.2	$	82.4
Amortization of deferred costs	$	11.4	$	21.1	$	6.8	$	2.7	$	42.0