Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net income (loss)	$ (128,363)	$ 45,751	$ (270,618)	$ (388,264)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax	1,346	(439)	(224)	10,586
Derivatives Qualifying as Hedges, Tax benefit	(486)	157	82	(3,810)
Derivatives Qualifying as Hedges, Adjustment, Net of Tax	860	(282)	(142)	6,776
Pension and Other Postretirement Benefit Plans, Total comprehensive income (loss) before tax	1,277	(989)	4,981	(5,957)
Pension and Other Postretirement Benefit Plans, Tax impact	(458)	374	(1,791)	2,162
Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	819	(615)	3,190	(3,795)
Available-for-sale Securities Adjustment, Total comprehensive income (loss) before tax	1,136	(869)	7,648	(377)
Available-for-sale Securities, Tax benefit	(448)	314	(2,795)	137
Available-for-sale Securities Adjustment, Net of Tax	688	(555)	4,853	(240)
Total other comprehensive income (loss)	2,367	(1,452)	7,901	2,741
Total comprehensive income (loss)	$ (125,996)	$ 44,299	$ (262,717)	$ (385,523)