Comprehensive Income (Accumulated Other Comprehensive Loss, Net of Tax) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	$ (483,576)	$ (386,963)
Other comprehensive income before reclassifications	(359)	(487)
Amounts reclassified from accumulated other comprehensive loss	20,164	12,629
Recognition of net actuarial loss for pension settlement costs	24,992
Net current-period other comprehensive income (loss)	44,797	12,142
Balance, ending	(438,779)	(374,821)
Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	(697,874)	(575,163)
Other comprehensive income before reclassifications	133
Amounts reclassified from accumulated other comprehensive loss	30,948	22,268
Recognition of net actuarial loss for pension settlement costs	40,309
Net current-period other comprehensive income (loss)	71,390	22,268
Balance, ending	(626,484)	(552,895)
Postretirement Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	(74,264)	(41,811)
Other comprehensive income before reclassifications	(267)
Amounts reclassified from accumulated other comprehensive loss	1,575	(1,898)
Net current-period other comprehensive income (loss)	1,308	(1,898)
Balance, ending	(72,956)	(43,709)
Deferred Taxes On Pension And OPEB Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	288,712	230,161
Other comprehensive income before reclassifications	(227)	(489)
Amounts reclassified from accumulated other comprehensive loss	(12,359)	(7,741)
Recognition of net actuarial loss for pension settlement costs	(15,317)
Net current-period other comprehensive income (loss)	(27,903)	(8,230)
Balance, ending	260,809	221,931
All Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	(150)	(150)
Other comprehensive income before reclassifications	2	2
Net current-period other comprehensive income (loss)	2	2
Balance, ending	$ (148)	$ (148)