Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Transportation services revenue – third parties	$ 0.8	$ 1.0
Transportation services revenue – related parties	28.8	29.7
Total revenue	$ 29.6	$ 30.7