Revenue from Contracts with Customers - Contract Assets and Liabilities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Contract Assets, Current [Roll Forward]
Balance as of January 1, 2018	$ 0.0
Recognized in current year	23.4
Reclassified to accounts receivable	(22.1)
Impairment	0.0
Reclassification to/from long-term	0.8
Balance as of March 31, 2018	38.6
Contract Assets, Noncurrent [Roll Forward]
Balance as of January 1, 2018	0.0
Recognized in current year	0.0
Reclassified to accounts receivable	0.0
Impairment	0.0
Reclassification to/from short-term	(0.8)
Balance as of March 31, 2018	16.1
Contract Liabilities, Current [Roll Forward]
Balance as of January 1, 2018	0.0
Recognized in current year	8.4
Amounts in beginning balance reclassified to revenue	(14.1)
Current year amounts reclassified to revenue	(0.3)
Other	0.0
Reclassification to/from long-term	2.5
Balance as of March 31, 2018	66.2
Contract Liabilities, Noncurrent [Roll Forward]
Balance as of January 1, 2018	0.0
Recognized in current year	0.2
Amounts in beginning balance reclassified to revenue	(0.2)
Current year amounts reclassified to revenue	0.0
Other	0.0
Reclassification to/from short-term	(2.5)
Balance as of March 31, 2018	$ 19.7