Segments (Reconciliation of Net Income (Loss) to EBITDA) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net income (loss)	$ (37.4)	$ (15.3)	$ 319.9
Interest and debt expense, net	(132.1)	(133.6)	(115.4)
(Gain) loss on modification/extinguishment of debt	7.5	(0.1)	0.0
(Provision) benefit for income taxes	0.2	0.4	0.3
Depreciation, amortization and accretion	244.2	237.4	195.8
EBITDA	346.6	356.0	631.4
CMLP
Segment Reporting Information [Line Items]
Net income (loss)	(44.0)	(23.4)	310.6
Interest and debt expense, net	(132.1)	(133.6)	(115.4)
(Gain) loss on modification/extinguishment of debt	7.5	(0.1)	0.0
(Provision) benefit for income taxes	0.1	(0.1)	0.3
Depreciation, amortization and accretion	258.4	251.5	209.9
EBITDA	$ 354.1	$ 361.5	$ 636.2