Revenue from Contracts with Customers (Tables)

6 Months Ended

Jun. 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):



	June 30, 2018		December 31, 2017
Current contract assets	$	4.1	$	3.0
Noncurrent contract assets	$	—	$	2.8
Current contract liabilities (deferred revenue)	$	76.6	$	71.9
Noncurrent contract liabilities (deferred revenue)	$	23.2	$	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	—			27.6
Decrease due to amortization of deferred revenue that was included in the beginning contract liability balance	—			(43.0		)
Decrease due to amortization of deferred revenue that was added during the period	—			(7.9		)
Decrease due to transfer to receivables during the period	(1.7		)	—
Balance as of June 30, 2018	$	4.1		$	99.8

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

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



	Remaining 2018		2019		2020		2021 and Thereafter		Total
Amortization of contract liabilities	$	38.9	$	51.0	$	6.4	$	3.5	$	99.8
Amortization of deferred costs	$	23.4	$	21.6	$	6.0	$	2.4	$	53.4