Investments in Non-Consolidated Subsidiaries (Income Statement Disclosure) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 White Cliffs Pipeline, LLC [Member]	Dec. 31, 2012 White Cliffs Pipeline, LLC [Member]	Dec. 31, 2011 White Cliffs Pipeline, LLC [Member]	Sep. 30, 2013 Ngl Energy Partners Lp [Member]	Sep. 30, 2012 Ngl Energy Partners Lp [Member]
Summarized income statement information
Revenue				$ 133,310	$ 108,125	$ 66,097	$ 5,935,715	$ 2,371,524
Costs of products sold	1,020,100	874,885	1,144,439				5,478,361	2,182,263
Operating, general and administrative expenses				23,825	14,821	12,746	276,905	125,889
Depreciation and amortization expense				18,668	19,963	20,842	94,050	34,621
Net income				$ 90,817	$ 73,341	$ 32,509	$ 44,378	$ 5,405