Partners' Capital, Mezzanine Capital and Distributions (Narrative) (Details) $ / shares in Units, $ in Millions						2 Months Ended	3 Months Ended
	Feb. 14, 2019 shares	Nov. 14, 2018 shares	Aug. 14, 2018 shares	May 15, 2018 shares	Sep. 01, 2017 USD ($) buyer $ / shares shares	Feb. 28, 2019 shares	Mar. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 shares
Temporary Equity [Line Items]
Common units outstanding (in units)							122,579,218	122,579,218
Number of convertible preferred units issued (in units)							24,972,598	22,438,022
Common Class A | Partners’ Capital
Temporary Equity [Line Items]
Common units outstanding (in units)							122,539,221
Common Class B | Partners’ Capital
Temporary Equity [Line Items]
Common units outstanding (in units)							39,997
Class A Convertible Preferred Stock Units
Temporary Equity [Line Items]
Preferred units, cumulative cash distributions | $							$ 18.4
Distributions paid-in-kind (in units)	534,576	523,132	511,934	500,976		364,180	534,576
Stock dividend rate per unit (in dollars per unit) | $ / shares							$ 0.2458
Class A Convertible Preferred Stock Units | Quarterly Rate
Temporary Equity [Line Items]
Stock dividend rate per unit (in dollars per unit) | $ / shares							0.7374
Class A Convertible Preferred Stock Units | In Arrears At Annual Rate
Temporary Equity [Line Items]
Stock dividend rate per unit (in dollars per unit) | $ / shares							$ 2.9496
Private Placement | Class A Convertible Preferred Stock Units
Temporary Equity [Line Items]
Temporary equity, stock issued during period (in shares) | $					$ 750.0
Number of convertible preferred units issued (in units)					22,249,494
Cash purchase price per unit (in dollars per unit) | $ / shares					$ 33.71
Number of initial purchasers | buyer					2