Revenue from Contracts with Customers (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

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

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

	December 31, 2018		December 31, 2017
Current contract assets	$	4.0	$	3.0
Noncurrent contract assets	$	—	$	2.8
Current contract liabilities (deferred revenue)	$	56.9	$	71.9
Noncurrent contract liabilities (deferred revenue)	$	20.5	$	51.2

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
Revenue recognized in advance of right to bill customer	2.2			—
Increase due to cash received	—			49.4
Decrease due to amortization of deferred revenue that was included in the beginning contract liability balance	—			(72.0		)
Decrease due to amortization of deferred revenue that was added during the period	—			(23.1		)
Decrease due to transfer to receivables during the period	(4.0		)	—
Balance as of December 31, 2018	$	4.0		$	77.4

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

Expected future amortization of our contract liabilities and deferred costs recorded as of December 31, 2018 is set forth in the table below (in millions):

	2019		2020		2021		2022 and Thereafter		Total
Amortization of contract liabilities	$	57.0	$	11.7	$	7.2	$	1.5	$	77.4
Amortization of deferred costs	$	23.8	$	9.4	$	2.4	$	1.5	$	37.1