Revenue Recognition (Tables)

3 Months Ended

Mar. 31, 2018

Revenue from Contract with Customer [Abstract]

Contract with Customer, Asset and Liability

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



	March 31, 2018		December 31, 2017
Current contract assets	$	3.7	$	3.0
Noncurrent contract assets	$	1.5	$	2.8
Current contract liabilities (deferred revenue)	$	78.0	$	71.9
Noncurrent contract liabilities (deferred revenue)	$	42.1	$	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	—			24.6
Decrease due to amortization of deferred revenue that was included in the beginning contract liability balance	—			(24.8		)
Decrease due to amortization of deferred revenue that was added during the period	—			(2.8		)
Decrease due to transfer to receivables during the period	(0.6		)
Balance as of March 31, 2018	$	5.2		$	120.1

Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction

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



	Remaining 2018		2019		2020		2021 and Thereafter		Total
Amortization of contract liabilities	$	59.9	$	50.7	$	6.2	$	3.3	$	120.1
Amortization of deferred costs	$	32.2	$	19.7	$	5.2	$	2.0	$	59.1