Partners' Capital and Distributions (Schedule of Capital Units) (Details)	6 Months Ended
	Jun. 30, 2018 shares
Increase (Decrease) in Partners' Capital [Roll Forward]
Limited partner units outstanding on January 1, 2018 (in shares)	228,024,556
Limited partner units outstanding on March 31, 2018 (in shares)	228,195,160
Management [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
During 2018–Other (in shares)	168,913
Director [Member]
Increase (Decrease) in Partners' Capital [Roll Forward]
During 2018–Other (in shares)	1,691