Reconciliation of Segment Information, Revenue and Other Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue From External Customers									$ 1,980,592	$ 2,081,873	$ 2,930,172
Gain (Loss) on Hedging Activity									(141,021)	392,942	23,193
Earnings Before Income Taxes:
Income (Loss) from Continuing Operations before Income Taxes, Domestic									(525,955)	(475,705)	180,151
Other Income									167,306	144,351	207,460
Gain (Loss) on Disposition of Assets									19,498	74,173	43,198
Sales	$ 390,398	$ 688,590	$ 602,772	$ 235,251	$ 478,864	$ 631,979	$ 503,825	$ 715,740	2,026,375	2,693,339	3,204,023
Total Reportable Business Segments
Earnings Before Income Taxes:
Income (Loss) from Continuing Operations before Income Taxes, Domestic									(248,132)	(273,863)	620,682
Gas Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Gain (Loss) on Hedging Activity									(141,021)	392,942	23,193
Earnings Before Income Taxes:
Income (Loss) from Continuing Operations before Income Taxes, Domestic									(378,840)	(678,857)	189,714
Corporate and Other [Member]
Earnings Before Income Taxes:
Income (Loss) from Continuing Operations before Income Taxes, Domestic									(85,923)	66,713	(119,473)
Other Segments [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Gain (Loss) on Hedging Activity									0	0	0
Earnings Before Income Taxes:
Income (Loss) from Continuing Operations before Income Taxes, Domestic									(277,399)	(200,304)	(438,073)
Excludes Gas Segment [Member]
Earnings Before Income Taxes:
Interest Income (Expense), Net and Other Non-operating Activity									(191,476)	(199,266)	(223,333)
Fees for Disposing Non-core Assets									(424)	(1,538)	2,458
Corporate Adjustments And Eliminations [Member]
Earnings Before Income Taxes:
Gain (Loss) Estimates on Extinguishment of Debt									0	(67,751)	(95,267)
Intersegment Eliminations [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Gain (Loss) on Hedging Activity									0	0	0
Earnings Before Income Taxes:
Income (Loss) from Continuing Operations before Income Taxes, Domestic									(424)	(1,538)	(2,458)
UNITED STATES
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue From External Customers									1,799,336	1,822,452	2,713,833
Asia [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue From External Customers									109,312	106,954	66,912
Europe [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue From External Customers									40,704	112,844	121,909
South America [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue From External Customers									25,406	28,060	19,013
CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue From External Customers									$ 5,834	$ 11,563	$ 8,505