Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (Schedule of Reclassifications) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
comprehensive income reclassifications [Line Items]
Revenues	$ 825,502	$ 1,039,651
Interest and investment income	2,836	1,021
Total before tax	(124,680)	(19,670)
Benefit from income taxes	(54,631)	(21,079)
Net of tax	(70,049)	1,409
reclassification out of accumulated other comprehensive income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
comprehensive income reclassifications [Line Items]
Amortization of prior service credits	2,908
Amortization of actuarial gains (losses) net	(4,862)
Total before tax	(1,954)
Benefit from income taxes	703
Net of tax	(1,251)
reclassification out of accumulated other comprehensive income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
comprehensive income reclassifications [Line Items]
Interest and investment income	(59)
Benefit from income taxes	21
Net of tax	(38)
Commodity Contract [Member] | reclassification out of accumulated other comprehensive income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
comprehensive income reclassifications [Line Items]
Revenues	859
Benefit from income taxes	(309)
Net of tax	$ 550