Consolidated Statements Of Comprehensive Operations (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Net income	$ 3,344	$ 6,775	$ 100,108	$ 95,929
Unrecognized pension and postretirement benefit costs:
Net loss arising during period	0	0	(77,678)	(9,874)
Prior service benefit	0	0	0	26,605
Reclassification adjustments included in net income for amortization of:
Prior service benefit	(1,443)	(1,455)	(5,800)	(3,509)
Net loss	3,125	1,475	8,155	3,949
Net unrealized gains (losses) on marketable securities:
Net holding gains arising during period	8,158	2,173	7,555	6,415
Reclassification adjustments for net (gains) losses included in net income	(213)	(205)	1,350	(114)
Net losses on cash flow hedges:
Reclassification adjustment for interest expense included in net income	94	88	367	343
Total other comprehensive income (loss) before income taxes	9,721	2,076	(66,051)	23,815
Income tax benefit (expense) related to items of other comprehensive income (loss):
Unrecognized pension and postretirement benefit costs	(555)	(7)	29,586	(6,221)
Net unrealized losses on marketable securities	(1,559)	(360)	(1,762)	(1,226)
Losses on cash flow hedges	(45)	(33)	(215)	(126)
Total income tax benefit (expense)	(2,159)	(400)	27,609	(7,573)
Other comprehensive income (loss), net of tax	7,562	1,676	(38,442)	16,242
Comprehensive income	$ 10,906	$ 8,451	$ 61,666	$ 112,171