Consolidated Statements Of Comprehensive Operations (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net income	$ 30,894	$ 32,990	$ 34,238	$ 39,765	$ 98,012	$ 107,412
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	(1,437)	(1,450)	(2,880)	(2,905)	(5,787)	(4,282)
Net loss	2,860	1,778	5,985	3,253	9,237	4,940
Net unrealized gains (losses) on marketable securities:
Net holding gains (losses) arising during period	(2,341)	416	5,817	2,589	4,798	13,232
Reclassification adjustments for net (gains) losses included in net income	1,447	2	1,234	(203)	2,795	(490)
Net losses on cash flow hedges:
Reclassification adjustment for interest expense included in net income	95	88	189	176	374	348
Total other comprehensive income (loss) before income taxes	624	834	10,345	2,910	(66,261)	30,479
Income tax benefit (expense) related to items of other comprehensive income (loss):
Unrecognized pension and postretirement benefit costs	(541)	(124)	(1,096)	(131)	29,169	(6,306)
Net unrealized losses on marketable securities	189	(157)	(1,370)	(517)	(1,416)	(2,588)
Losses on cash flow hedges	(36)	(33)	(81)	(66)	(218)	(128)
Total income tax benefit (expense)	(388)	(314)	(2,547)	(714)	27,535	(9,022)
Other comprehensive income (loss), net of tax	236	520	7,798	2,196	(38,726)	21,457
Comprehensive income	$ 31,130	$ 33,510	$ 42,036	$ 41,961	$ 59,286	$ 128,869