Investments in Non-Consolidated Subsidiaries - Distributions received, by investment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Schedule of Equity Method Investments [Line Items]
Proceeds from Equity Method Investment, Dividends or Distributions	$ 16,421	$ 16,951
Return of and return on capital [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from Equity Method Investment, Dividends or Distributions	18,926	18,064
White Cliffs Pipeline L L C [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from Equity Method Investment, Dividends or Distributions	13,585	13,792
NGL Energy Partners LP [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from Equity Method Investment, Dividends or Distributions	5,341	4,272
Glass Mountain Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from Equity Method Investment, Dividends or Distributions	$ 0	$ 0