Equity Method Investments (Summarized Income Statement Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
White Cliffs Pipeline, LLC [Member]
Summarized income statement information
Revenue	$ 212,359		$ 206,395		$ 160,369
Costs of products sold	3,223		2,914		3,635
Operating, general and administrative expenses	35,672		30,370		19,431
Depreciation and amortization expense	35,439		34,105		23,257
Net income	138,032		139,000		114,045
Ngl Energy Partners Lp [Member]
Summarized income statement information
Revenue		$ 10,777,954		$ 14,504,581		$ 15,748,520
Costs of products sold		10,005,830		13,573,066		15,054,291
Operating, general and administrative expenses		523,902		576,805		436,959
Depreciation and amortization expense		211,841		221,067		162,443
Net income		$ (39,895)		$ 71,225		$ 15,059
Glass Mountain Pipeline Llc [Member]
Summarized income statement information
Revenue	29,502		38,526		30,398
Costs of products sold	463		3,392		757
Operating, general and administrative expenses	7,570		6,643		6,419
Depreciation and amortization expense	15,914		15,828		13,872
Net income	$ 5,548		$ 12,657		$ 9,344