Investments (Schedule Of Equity Method Investments) (Details) (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jan. 31, 2011
Balance at December 31, 2010	$ 177,451
Investments in affiliates	33,980
Advances to (distributions from) affiliates, net	(9,591)
Equity in comprehensive income (loss)	5,806
Balance at June 30, 2011	207,646
Balance at December 31, 2010	23,900
Balance at June 30, 2011	29,300
Knight Hawk [Member]
Balance at December 31, 2010	131,250
Advances to (distributions from) affiliates, net	(9,591)
Equity in comprehensive income (loss)	9,981
Balance at June 30, 2011	131,640
Balance at December 31, 2010	1,700
DKRW [Member]
Balance at December 31, 2010	21,961
Equity in comprehensive income (loss)	(1,079)
Balance at June 30, 2011	20,882
Balance at December 31, 2010	18,100
Balance at June 30, 2011	24,700
DTA [Member]
Balance at December 31, 2010	14,472
Investments in affiliates	2,910
Equity in comprehensive income (loss)	(2,207)
Balance at June 30, 2011	15,175
Tenaska [Member]
Balance at December 31, 2010	9,768
Investments in affiliates	5,500
Equity in comprehensive income (loss)	(2)
Balance at June 30, 2011	15,266
Balance at December 31, 2010	4,100
Balance at June 30, 2011	4,600
Millennium [Member]
Balance at December 31, 2010		25,000
Investments in affiliates	25,570
Equity in comprehensive income (loss)	(887)
Balance at June 30, 2011	$ 24,683	$ 25,000