Earnings Per Unit (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss from continuing operations		$ (38.6)	$ (4.6)	$ (16.8)	$ 16.4	$ 19.1	$ (16.0)	$ (51.2)	$ (2.9)	$ (43.6)	$ (51.0)	$ (31.3)
General partner’s interest in net loss from continuing operations										0.9	1.1	2.1
Net loss available to limited partners		$ (37.8)	$ (4.5)	$ (16.5)	$ 16.0	$ 17.7	$ (16.1)	$ (50.9)	$ (4.7)	$ (42.7)	$ (54.0)	$ (101.7)
Limited partners' interest basic net loss per unit from continuing operations		$ (0.48)	$ (0.06)	$ (0.21)	$ 0.20	$ 0.24	$ (0.20)	$ (0.64)	$ (0.04)	$ (0.55)	$ (0.64)	$ (0.40)
Limited partners' interest basic net loss per unit from discontinued operations						(0.01)	(0.01)	(0.01)	(0.02)	0.00	(0.05)	(0.91)
Limited partners’ interest basic net loss per unit		(0.48)	(0.06)	(0.21)	0.20	0.23	(0.21)	(0.65)	(0.06)	(0.55)	(0.69)	(1.31)
Limited partners' interest diluted net loss per unit from continuing operations		(0.48)	(0.06)	(0.21)	0.20	0.24	(0.20)	(0.64)	(0.04)	(0.55)	(0.64)	(0.40)
Limited partners' interest diluted net loss per unit from discontinued operations		0.00	0.00	0.00	0.00	(0.01)	(0.01)	(0.01)	(0.02)	0.00	(0.05)	(0.91)
Limited partners' interest diluted net loss per unit		$ (0.48)	$ (0.06)	$ (0.21)	$ 0.20	$ 0.23	$ (0.21)	$ (0.65)	$ (0.06)	$ (0.55)	$ (0.69)	$ (1.31)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount										100,000	200,000	200,000
Denominator for basic and diluted earnings per limited partner unit:
Weighted Average Number of Shares Outstanding, Basic and Diluted	[1]									78,212,136	77,943,992	77,598,950
Continuing Operations
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
General partner’s interest in net loss from continuing operations										$ (0.9)	$ (1.0)	$ (0.6)
Net loss available to limited partners										(42.7)	(50.0)	(30.7)
Discontinued Operations, Disposed of by Sale
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss available to limited partners										$ 0.0	$ (4.0)	$ (71.0)

[1] Total diluted weighted average limited partner units outstanding includes 0.1 million of potentially dilutive phantom units which would have been anti-dilutive for the year ended December 31, 2019 and 0.2 million potentially dilutive phantom units which would be anti-dilutive in the years ended December 31, 2018 and 2017.