Accumulated Other Comprehensive Income Amounts Reclassified (Details) (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
Marketable Securities:
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	$ 246			$ 88			$ 593
Unrealized Losses on Available-for-Sales Recognized in Earnings, before Tax	0			0			(313)
Reclassification adjustments for net (gains) losses included in net income	246		(1,447)	88		(1,234)	280		(2,795)
Tax effect on gain and loss from available-for-sale securities	(41)			(4)			(22)
Other Comprehensive Income (Loss), Reclassification Adjustment for Available-For-Sale Securities Included in Net Income, Net of Tax	205			84			258
Amortization of Pension and Postretirement Benefit Costs:
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)
Amortization of Prior Service Benefit and Net loss, before tax	(1,345)			(2,620)			(5,724)
Tax effect of the amortization of pension and postretirement benefit costs	511			1,081			2,294
Other comprehensive income (loss) reclassification adjustment on pension and other postretirement benefit plans, net of tax	(834)			(1,539)			(3,430)
Cash Flow Hedge Loss Reclassified to Earnings:
Cash Flow Hedge Loss Reclassified to Interest Expense	(101)			(202)			(398)
Reclassification adjustment for interest expense included in net income	(101)		(95)	(202)		(189)	(398)		(374)
Income tax expense on losses on cash flow hedges	38		36	90		81	140		218
Other Comprehensive Income (Loss), Reclassification Adjustment for Loss on Cash Flow Hedge Included in Net Income, Net of Tax	(63)			(112)			(258)
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 692			$ 1,567			$ 3,430

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