Revenue from Contracts with Customers - Contract Assets and Liabilities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Contract Assets, Current [Roll Forward]
Balance as of January 1, 2018	$ 0.0
Recognized in current year	42.2
Reclassified to accounts receivable	(47.8)
Impairment	0.0
Reclassification to/from long-term	16.8
Balance as of June 30, 2018	47.7
Contract Assets, Noncurrent [Roll Forward]
Recognized in current year	0.0
Reclassified to accounts receivable	0.0
Impairment	0.0
Reclassification to/from short-term	(16.8)
Balance as of June 30, 2018	0.1
Contract Liabilities, Current [Roll Forward]
Balance as of January 1, 2018	0.0
Recognized in current year	31.8
Amounts in beginning balance reclassified to revenue	(31.7)
Current year amounts reclassified to revenue	(8.5)
Other	1.7
Reclassification to/from long-term	7.4
Balance as of June 30, 2018	70.4
Contract Liabilities, Noncurrent [Roll Forward]
Balance as of January 1, 2018	0.0
Recognized in current year	0.3
Amounts in beginning balance reclassified to revenue	(0.5)
Current year amounts reclassified to revenue	0.0
Other	0.0
Reclassification to/from short-term	(7.4)
Balance as of June 30, 2018	$ 14.6