Consolidated Statements Of Comprehensive Operations (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net income	$ 51,789	$ 58,321	$ 86,027	$ 98,086	$ 91,480	$ 105,551
Unrecognized pension and postretirement benefit costs:
Net loss arising during period	0	0	0	0	(77,678)	(9,874)
Prior service benefit	0	0	0	0	0	26,605
Reclassification adjustments included in net income for amortization of:
Prior service benefit	(1,441)	(1,453)	(4,321)	(4,358)	(5,775)	(5,047)
Net loss	2,993	1,625	8,978	4,878	10,605	5,722
Net unrealized gains (losses) on marketable securities:
Net holding gains (losses) arising during period	6,169	(7,503)	11,986	(4,914)	18,470	(1,290)
Reclassification adjustments for net (gains) losses included in net income	(318)	1,284	916	1,081	1,193	601
Net losses on cash flow hedges:
Reclassification adjustment for interest expense included in net income	97	93	286	269	378	355
Total other comprehensive income (loss) before income taxes	7,500	(5,954)	17,845	(3,044)	(52,807)	17,072
Income tax benefit (expense) related to items of other comprehensive income (loss):
Unrecognized pension and postretirement benefit costs	(591)	(65)	(1,687)	(196)	28,643	(6,314)
Net unrealized gains (losses) on marketable securities	(1,201)	1,171	(2,571)	654	(3,788)	26
Losses on cash flow hedges	(36)	(35)	(117)	(101)	(219)	(132)
Total income tax benefit (expense)	(1,828)	1,071	(4,375)	357	24,636	(6,420)
Other comprehensive income (loss), net of tax	5,672	(4,883)	13,470	(2,687)	(28,171)	10,652
Comprehensive income	$ 57,461	$ 53,438	$ 99,497	$ 95,399	$ 63,309	$ 116,203