Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Contingent tax liability for uncertain tax positions	$ 8.3
Effective tax rate (as a percent)	18.30%	(32.10%)	16.20%
Net deferred tax liability	$ 220.9	$ 224.6
Unrecognized tax benefits	0.4	8.3	$ 0.0
Net operating loss carryovers	0.7	1.3
Distributions to members	$ 0.0	$ 75.3	$ 48.6
Federal statutory rate (as a percent)	21.00%	35.00%	35.00%
Tax benefit from reform	$ 110.9
Effect of Tax Cuts and Jobs Act (as a percent)	(0.00%)	(57.60%)	(0.00%)
Receipt from finalization of tax distribution	$ 1.8	$ 0.0	$ 0.0
Non-cash Transaction [Member]
Income Taxes [Line Items]
Other	$ 292.5