Supplemental Cash Flow Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Cash:
Interest paid, net of capitalized interest	[1]	$ 66.1	$ 42.8
Income taxes paid, net of refunds		0.3
Non-cash investing activities:
Deadstock commodity inventory transferred to property, plant and equipment		17.5	1.7
Transfers from materials and supplies inventory to property, plant and equipment		1.1	0.4
Contribution of property, plant and equipment to investments in unconsolidated affiliates			16.0
Change in ARO liability and property, plant and equipment		7.4	2.1
Non-cash financing activities:
Reduction of Owner's Equity related to accrued dividends on unvested equity awards under share compensation arrangements		3.6	3.3
Accretion of deemed dividends on Series A Preferred Stock		7.9	7.0
Impact of accounting standard adoption recorded in retained earnings			5.2
Non-cash balance sheet movements related to acquisition of related party:
Noncontrolling interest			1.2
Lease liabilities arising from recognition of right-of-use assets:
Operating lease		0.4
Finance lease		1.5
Retained Earnings [Member]
Non-cash investing activities:
Impact of capital expenditure accruals on property, plant and equipment		$ (38.8)	(22.3)
Non-cash financing activities:
Impact of accounting standard adoption recorded in retained earnings			$ 5.2

[1] Interest capitalized on major projects was $18.9 million and $9.6 million for the three months ended March 31, 2019 and 2018.