Equity Investments And Membership Interests In Joint Ventures (Schedule Of Equity Method Investments) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2013	Dec. 31, 2012
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012	$ 242,215
Advances to affiliates, net	3,493
Equity in comprehensive income (loss)	(2,314)
Impairment of equity investment	(15,264)
Balance at June 30, 2013	232,758
Notes receivable from investees:	42,501	43,828
Knight Hawk [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012	149,063
Advances to affiliates, net	(3,713)
Equity in comprehensive income (loss)	(7,812)
Impairment of equity investment
Balance at June 30, 2013	153,162
Notes receivable from investees:
DKRW [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012	15,515
Advances to affiliates, net
Equity in comprehensive income (loss)	1,241
Impairment of equity investment
Balance at June 30, 2013	14,274
Notes receivable from investees:	42,501	38,680
DTA [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012	15,462
Advances to affiliates, net	1,944
Equity in comprehensive income (loss)	2,629
Impairment of equity investment
Balance at June 30, 2013	14,777
Notes receivable from investees:
Tenaska [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012	15,264
Advances to affiliates, net
Equity in comprehensive income (loss)
Impairment of equity investment	(15,264)
Balance at June 30, 2013
Notes receivable from investees:		5,148
Millennium [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012	32,214
Advances to affiliates, net	3,441
Equity in comprehensive income (loss)	1,347
Impairment of equity investment
Balance at June 30, 2013	34,308
Notes receivable from investees:
Tongue River [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012	14,697
Advances to affiliates, net	1,821
Equity in comprehensive income (loss)	281
Impairment of equity investment
Balance at June 30, 2013	16,237
Notes receivable from investees:

This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 9

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 6

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 19

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.12)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 11

-Article 7

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