Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Current income tax provision	$ 1.2	$ 0.8
Deferred income tax provision	5.8	2.2
Total income tax provision	7.0	3.0
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected income tax provision based on federal statutory rate	4.1	0.4
State income taxes expense, net of federal tax benefit	0.5	0.0
Income tax expense from partnership	1.0	0.5
Unit-based compensation	1.6	2.3
Other	(0.2)	(0.2)
Total income tax provision	$ 7.0	$ 3.0