Consolidated Statements Of Comprehensive Operations (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net income	$ 50,565	$ 51,789	$ 87,392	$ 86,027	$ 92,211	$ 91,480
Unrecognized pension and postretirement benefit costs:
Net loss arising during period	0	0	0	0	(2,109)	(77,678)
Reclassification adjustments included in net income for amortization of:
Prior service benefit	(1,369)	(1,441)	(4,169)	(4,321)	(5,610)	(5,775)
Net loss	2,903	2,993	8,323	8,978	11,316	10,605
Net unrealized gains/losses on marketable securities:
Net holding gains arising during period	4,300	6,169	8,861	11,986	6,802	18,470
Reclassification adjustments for net (gains) losses included in net income	(199)	(318)	(287)	916	(161)	1,193
Net losses on cash flow hedges:
Reclassification adjustment for interest expense included in net income	104	97	306	286	405	378
Total other comprehensive income (loss) before income taxes	5,739	7,500	13,034	17,845	10,643	(52,807)
Income tax benefit (expense) related to items of other comprehensive income (loss):
Unrecognized pension and postretirement benefit costs	(469)	(591)	(1,550)	(1,687)	(1,327)	28,643
Net unrealized gains on marketable securities	(796)	(1,201)	(1,433)	(2,571)	(1,300)	(3,788)
Losses on cash flow hedges	(39)	(36)	(129)	(117)	(143)	(219)
Total income tax benefit (expense)	(1,304)	(1,828)	(3,112)	(4,375)	(2,770)	24,636
Other comprehensive income (loss), net of tax	4,435	5,672	9,922	13,470	7,873	(28,171)
Comprehensive income	$ 55,000	$ 57,461	$ 97,314	$ 99,497	$ 100,084	$ 63,309