Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended								9 Months Ended
	Oct. 21, 2020	Apr. 01, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019
Subsequent Event [Line Items]
Distributions paid per limited partner unit (in dollars per share)			$ 0.4600	$ 0.4600	$ 0.4600	$ 0.4600	$ 0.4450	$ 0.4300	$ 0.4150	$ 0.4000	$ 1.3800	$ 1.2900
Preferred Units
Subsequent Event [Line Items]
Distributions paid per limited partner unit (in dollars per share)		$ 0.2363
Partnership Interests Restructuring Agreement | General Partner SPLC
Subsequent Event [Line Items]
Distribution to general partner, waived		$ 20
Subsequent Event | Common Units
Subsequent Event [Line Items]
Distributions paid per limited partner unit (in dollars per share)	$ 0.4600