v3.6.0.2
Quarterly Financial Data (Unaudited) (Details) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Quarterly Financial Data                      
Total revenues $ 319 $ 308 $ 293 $ 300 $ 292 $ 282 $ 275 $ 263 $ 1,220 $ 1,112 $ 600
Operating expenses 128 113 113 117 135 117 115 101 471 468 324
Operating income 123 127 118 119 97 100 97 99 487 393 164
Net earnings (loss) 73 81 76 85 59 65 60 65 315 249 56
Limited partners’ interest in net earnings $ 32 $ 48 $ 47 $ 60 $ 46 $ 54 $ 49 $ 50 $ 187 $ 199 $ 56
Net earnings (loss) per limited partner unit:                      
Common - basic (dollars per unit) $ 0.31 [1] $ 0.46 [1] $ 0.48 [1] $ 0.64 [1] $ 0.49 [1] $ 0.62 [1] $ 0.60 [1] $ 0.63 [1] $ 1.87 [1] $ 2.33 [1] $ 0.96
Common - diluted (dollars per unit) $ 0.31 [1] $ 0.46 [1] $ 0.48 [1] $ 0.64 [1] $ 0.49 [1] $ 0.62 [1] $ 0.60 [1] $ 0.63 [1] $ 1.87 [1] $ 2.33 [1] $ 0.96
[1] The sum of four quarters may not equal annual results due to rounding or the quarterly number of units outstanding.