Investments (Schedule Of Equity Method Investments) (Details) (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Jan. 31, 2011
Balance at December 31, 2010	$ 177,451
Investments in affiliates	43,489
Advances to (distributions from) affiliates, net	(5,156)
Equity in comprehensive income (loss)	8,900
Balance at September 30, 2011	224,684
Balance at December 31, 2010	23,900
Balance at September 30, 2011	33,194
Knight Hawk [Member]
Balance at December 31, 2010	131,250
Advances to (distributions from) affiliates, net	(11,450)
Equity in comprehensive income (loss)	15,807
Balance at September 30, 2011	135,607
Balance at December 31, 2010	1,700
DKRW [Member]
Balance at December 31, 2010	21,961
Equity in comprehensive income (loss)	(1,631)
Balance at September 30, 2011	20,330
Balance at December 31, 2010	18,100
Balance at September 30, 2011	28,417
DTA [Member]
Balance at December 31, 2010	14,472
Advances to (distributions from) affiliates, net	4,394
Equity in comprehensive income (loss)	(3,713)
Balance at September 30, 2011	15,153
Tenaska [Member]
Balance at December 31, 2010	9,768
Investments in affiliates	5,500
Equity in comprehensive income (loss)	(2)
Balance at September 30, 2011	15,266
Balance at December 31, 2010	4,100
Balance at September 30, 2011	4,777
Millennium [Member]
Balance at December 31, 2010		25,000
Investments in affiliates	25,000
Advances to (distributions from) affiliates, net	1,900
Equity in comprehensive income (loss)	(1,561)
Balance at September 30, 2011	25,339	25,000
Tongue River [Member]
Investments in affiliates	12,989
Balance at September 30, 2011	$ 12,989