Accumulated Other Comprehensive Loss (Details) (USD $) In Thousands, unless otherwise specified			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Reclassification out of Accumulated Other Comprehensive Income Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Change in the fair value of interest rate swaps	$ (601)	$ 0
Qualified pension and post-retirement healthcare plans	(159,178)	(255,989)
Total accumulated other comprehensive loss	(159,779)	(255,989)
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Amortization of actuarial loss			12,983	[1]
Plan settlement			1,683	[1]
Total employee benefit amounts reclassified from accumulated other comprehensive loss			14,666
Tax expense			(4,696)
Total employee benefit amounts reclassified from accumulated other comprehensive loss, net			$ 9,970

[1] These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. See note (11) "Employee Benefit Plans" for details.