Income Taxes - Significant Components of Deferred Tax Assets and Liabilities and Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Interest expense	$ 70.7	$ 73.6
Federal net operating loss	0.9	1.4
State net operating loss carry forwards	0.2	0.0
Investment in partnerships	164.1	182.0
Intangible assets	0.3	0.5
Employee compensation	4.4	6.2
Other	1.8	2.0
Cash flow hedge	6.2	4.7
Total deferred tax assets	248.6	270.4
Deferred tax liabilities:
Investments	5.0	0.3
Net deferred tax assets	243.6	270.1
Federal
Deferred tax liabilities:
Operating loss carryforwards	$ 4.4	$ 0.2
Federal | Minimum
Deferred tax liabilities:
Expiration period of operating loss carryforwards	5 years	5 years
Federal | Maximum
Deferred tax liabilities:
Expiration period of operating loss carryforwards	7 years	20 years