Consolidated Statements Of Comprehensive Operations (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended			12 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012
Net income	$ 29,193		$ 30,894	$ 36,827		$ 34,238	$ 93,435		$ 98,012
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	(1,400)	[1]	(1,437)	(2,800)	[1]	(2,880)	(5,682)	[1]	(5,787)
Net loss	2,745	[1]	2,860	5,420	[1]	5,985	11,406	[1]	9,237
Net unrealized gains (losses) on marketable securities:
Net holding gains (losses) arising during period	(2,232)		(2,341)	4,561		5,817	8,671		4,798
Reclassification adjustments for net (gains) losses included in net income	(246)		1,447	(88)		1,234	(280)		2,795
Net losses on cash flow hedges:
Reclassification adjustment for interest expense included in net income	101		95	202		189	398		374
Total other comprehensive income (loss) before income taxes	(1,032)		624	7,295		10,345	12,404		(66,261)
Income tax benefit (expense) related to items of other comprehensive income (loss):
Unrecognized pension and postretirement benefit costs	(511)		(541)	(1,081)		(1,096)	(1,449)		29,169
Net unrealized (gains) losses on marketable securities	650		189	(637)		(1,370)	(1,705)		(1,416)
Losses on cash flow hedges	(38)		(36)	(90)		(81)	(140)		(218)
Total income tax benefit (expense)	101		(388)	(1,808)		(2,547)	(3,294)		27,535
Other comprehensive income (loss), net of tax	(931)		236	5,487		7,798	9,110		(38,726)
Comprehensive income	$ 28,262		$ 31,130	$ 42,314		$ 42,036	$ 102,545		$ 59,286

[1] These items are included in the computation of net periodic benefit cost. See Note H, Employee Benefits, for additional information.