Equity-Method Investments (Details) (USD $)	3 Months Ended		9 Months Ended			1 Months Ended	9 Months Ended		1 Months Ended	9 Months Ended		7 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Feb. 28, 2011 SPN Resources [Member]	Sep. 30, 2010 SPN Resources [Member]	Dec. 31, 2010 SPN Resources [Member]	Feb. 28, 2011 DBH [Member]	Sep. 30, 2010 DBH [Member]	Dec. 31, 2010 DBH [Member]	Sep. 30, 2011 DOH [Member]	Mar. 31, 2011 DOH [Member]	Sep. 30, 2011 DOR [Member]
Equity-Method Investments (Textual) [Abstract]
Equity-method investments	$ 71,506,000		$ 71,506,000		$ 59,322,000			$ 43,600,000			$ 13,800,000	$ 69,700,000
Earnings from equity-method investments, net	8,198,000	3,030,000	13,724,000	9,185,000		200,000	3,900,000		900,000	5,100,000		12,400,000
Cash distributions received from equity-method investment							8,400,000					1,200,000
Receivable from equity method investment								3,200,000			1,400,000	11,400,000		5,300,000
Revenue from equity-method investment						$ 300,000	$ 11,100,000		$ 900,000	$ 2,500,000		$ 31,400,000
Equity-method ownership percentage													10.00%