Revenue Recognition - Contract Balances (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Movement in Deferred Revenue [Roll Forward]
Beginning balance	$ 5.5
Ending balance	8.0
Third Parties
Movement in Deferred Revenue [Roll Forward]
Beginning balance	5.5
Transition Adjustment	0.0
Additions	10.0
Reductions	7.5
Ending balance	8.0
Related Parties
Movement in Deferred Revenue [Roll Forward]
Beginning balance	13.9
Transition Adjustment	(4.5)
Additions	3.1
Reductions	9.9
Ending balance	$ 2.6