Equity Method Invesments (Summarized Balance Sheet Information) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
White Cliffs Pipeline, LLC [Member]
Current assets	$ 54,091		$ 35,623
Property, plant and equipment, net	509,068		471,179
Goodwill	17,000		17,000
Other intangible assets, net	11,974		16,043
Total assets	592,133		539,845
Current liabilities	9,491		11,108
Members’ equity	582,642		528,737
Total liabilities and members’ equity	592,133		539,845
Glass Mountain Pipeline LLC [Member]
Current assets	7,856		8,810
Property, plant and equipment, net	205,920		215,876
Total assets	213,776		224,686
Current liabilities	1,036		2,643
Other liabilities	28		42
Members’ equity	212,712		222,001
Total liabilities and members’ equity	$ 213,776		$ 224,686
Ngl Energy Partners Lp [Member]
Current assets		$ 1,276,919		$ 2,585,053
Property, plant and equipment, net		1,845,112		1,433,313
Goodwill		1,490,928		1,170,490
Other intangible assets, net		1,836,878		1,362,823
Total assets		6,449,837		6,551,679
Current liabilities		852,170		1,759,980
Long-term debt		3,093,694		2,437,351
Other noncurrent liabilities		17,679		39,518
Members’ equity		2,486,294		2,314,830
Total liabilities and members’ equity		$ 6,449,837		$ 6,551,679