Supplemental Cash Flow Information (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 01, 2017
Cash:
Interest paid, net of capitalized interest	[1]			$ 149.6	$ 164.1
Income taxes paid, net of refunds				(0.5)	(67.4)
Non-cash investing activities:
Deadstock commodity inventory transferred to property, plant and equipment				39.4	8.3
Transfers from materials and supplies inventory to property, plant and equipment				8.9	2.8
Contribution of property, plant and equipment to investments in unconsolidated affiliates				16.0	1.0
Change in ARO liability and property, plant and equipment due to revised cash flow estimate				1.2	3.1
Non-cash financing activities:
Reduction of Owner's Equity related to accrued dividends on unvested equity awards under share compensation arrangements		$ 10.3	$ 7.0	10.3	7.0
Accretion of deemed dividends on Series A Preferred Stock		7.4	6.5	21.5	19.0
Impact of accounting standard adoption recorded in retained earnings				5.2	56.1
Non-cash balance sheet movements related to assets held for sale (See Note 4 - Newly-Formed Joint Ventures, Acquisitions and Divestitures):
Trade receivables				8.8
Inventories				5.5
Property, plant and equipment, net				151.4
Accounts payable and accrued liabilities				(1.7)
Non-cash balance sheet movements related to the purchase of noncontrolling interests in subsidiary (See Note 4 - Newly-Formed Joint Ventures, Acquisitions and Divestitures):
Additional paid-in capital					(13.7)
Deferred tax liability					13.7
Non-cash balance sheet movements related to the TRC/TRP Merger:
Additional paid-in capital			0.3		0.3
Deferred tax liability			(0.3)		(0.3)
Non-cash balance sheet movements related to acquisition of related party:
Noncontrolling interest				1.1
Permian Acquisition [Member]
Non-cash balance sheet movements related to the Permian Acquisition (See Note 4 - Newly-Formed Joint Ventures, Acquisitions and Divestitures):
Potential earn-out payments of acquisition date fair value		$ 416.3	$ 416.3	416.3	416.3	$ 416.3
Retained Earnings [Member]
Non-cash investing activities:
Impact of capital expenditure accruals on property, plant and equipment				283.9	118.3
Non-cash financing activities:
Impact of accounting standard adoption recorded in retained earnings				$ 5.2	$ 56.1

[1] Interest capitalized on major projects was $30.8 million and $8.3 million for the nine months ended September 30, 2018 and 2017.