Employee Benefits, Summary of Activity in LTIP Incentive Compensation Plan (Details) - LTIP - Phantom Share Units (PSUs) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) yr $ / shares shares	Dec. 31, 2018 USD ($) yr $ / shares shares	Dec. 31, 2017 USD ($) yr shares	Jul. 17, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding balance, beginning (in units) | shares	889,702	972,895
Granted (in units) | shares	0	651,531
Paid (in units) | shares	(520,753)	(677,169)
Forfeited (in units) | shares	(21,493)	(57,555)
Outstanding balance, ending (in units) | shares	347,456	889,702	972,895
Unit Appreciation Rights and All Unit-Based Incentive Compensation Plans, Units, Fair Value [Abstract]
Outstanding balance, beginning | $	$ 11.2	$ 13.1
Granted | $	0.0	8.6
Paid | $	(6.7)	(8.9)
Forfeited | $	0.0	0.0
Outstanding balance, ending | $	$ 4.5	$ 11.2	$ 13.1
Unit Appreciation Rights and All Unit-Based Incentive Compensation Plans, Units, Weighted-Average Vesting Period [Abstract]
Outstanding balance, beginning | yr	1.2	1.0
Granted | yr	0	2.3
Outstanding balance, ending | yr	0.6	1.2	1.0
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized | shares				3,525,000
Phantom Units per unit Value after Purchase Transaction | $ / shares	$ 12.06
Compensation expense | $	$ 4.6	$ 7.3	$ 7.8
Total estimated remaining unrecognized compensation expense related to the Phantom Common Units | $	$ 1.0	$ 5.6
Share-based Compensation Arrangement by Share-based Payment Award, Shares Purchased for Award | shares		17,980
Share-based Compensation Arrangement by Share-based Payment Award, Per Share Weighted Average Price of Shares Purchased | $ / shares		$ 11.15