Investments - Summary of Selected Financial Information for Epic Gas (Details) - Epic Gas - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Total assets				$ 555.7
Total liabilities				312.6
Total equity				243.1
Net gains (losses)	$ 0.9	$ (16.4)	$ (15.9)	$ (3.7)	$ (14.5)