Accumulated Other Comprehensive Loss (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Total employee benefit amounts reclassified from accumulated other comprehensive loss, net of tax				$ 6,516
Qualified Pension [Member]
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Amortization of actuarial loss	(1,188)		(525)	(2,344)		(1,042)
Plan Settlement	(1,014)		0	(1,014)		(356)
Post-retirement Healthcare [Member]
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Amortization of actuarial loss	(2,235)		(1,682)	(4,470)		(3,364)
Plan Settlement	0		0			0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Amortization of actuarial loss	3,423	[1]		6,814	[1]
Plan Settlement	1,014	[1]		1,014	[1]
Total employee benefit amounts reclassified from accumulated other comprehensive loss	4,437			7,828
Tax on employee benefit amounts reclassified from accumulated other comprehensive loss	(669)			(1,312)
Total employee benefit amounts reclassified from accumulated other comprehensive loss, net of tax	$ 3,768			$ 6,516

[1] These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See note (7) "Employee Benefit Plans" for details.