Revenue Recognition - Impact of Adoption (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									$ 468.6
Lease revenue - related parties									56.1
Operations and maintenance – related parties									54.4	$ 45.6	$ 40.0
Operations and maintenance – third parties									107.5	104.1	76.9
Cost of product sold - related parties									25.3	0.0	0.0
Cost of product sold - third parties									7.4	0.0	0.0
Net income	$ 148.0	$ 154.2	$ 115.4	$ 64.8	$ 102.5	$ 99.5	$ 91.7	$ 98.1	482.4	391.8	377.5
Deferred revenue – related parties	2.6				$ 13.9				2.6	13.9
Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									30.7	0.0	0.0
Related Parties
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Lease revenue - related parties									56.1	56.3	13.1
Related Parties | Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									28.5	0.0	0.0
Related Parties | Transportation, Terminaling And Storage Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									228.5	178.2	188.3
Third Parties | Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									2.2	0.0	0.0
Third Parties | Transportation, Terminaling And Storage Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									209.4	$ 235.6	$ 251.5
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Lease revenue - related parties									106.5
Operations and maintenance – related parties									46.8
Operations and maintenance – third parties									112.1
Cost of product sold - related parties									0.0
Cost of product sold - third parties									5.5
Net income									487.0
Calculated under Revenue Guidance in Effect before Topic 606 | Related Parties | Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									0.0
Calculated under Revenue Guidance in Effect before Topic 606 | Related Parties | Transportation, Terminaling And Storage Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									183.4
Calculated under Revenue Guidance in Effect before Topic 606 | Third Parties | Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									0.0
Calculated under Revenue Guidance in Effect before Topic 606 | Third Parties | Transportation, Terminaling And Storage Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									209.2
Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue – related parties	2.5								2.5
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Lease revenue - related parties									(50.4)
Operations and maintenance – related parties									7.6
Operations and maintenance – third parties									(4.6)
Cost of product sold - related parties									25.3
Cost of product sold - third parties									1.9
Net income									(4.6)
Deferred revenue – related parties	$ 0.1								0.1
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Related Parties | Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									28.5
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Related Parties | Transportation, Terminaling And Storage Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									45.1
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Third Parties | Product Revenue
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									2.2
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606 | Third Parties | Transportation, Terminaling And Storage Services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue from contract with customer									$ 0.2