Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Total amounts reclassified from accumulated other comprehensive income, net	$ (37,152)	$ (73,288)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Total reclassified from accumulated other comprehensive income	33,053	$ 66,105
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent | Minimum
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Actuarial loss, amortization period		7 months 24 days
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent | Maximum
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Actuarial loss, amortization period		11 years 5 months 19 days
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Total reclassified from accumulated other comprehensive income	(89,020)	$ (177,796)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent | Minimum
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Unrecognized prior service credit, amortization period		10 months 13 days
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent | Maximum
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Unrecognized prior service credit, amortization period		23 years 10 months 28 days
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment Attributable to Parent
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Total reclassified from accumulated other comprehensive income	(55,967)	$ (111,691)
Tax benefit	18,452	37,676
Total amounts reclassified from accumulated other comprehensive income, net	(37,515)	(74,015)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent
ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncome [Line Items]
Total reclassified from accumulated other comprehensive income	608	1,216
Tax benefit	(245)	(489)
Total amounts reclassified from accumulated other comprehensive income, net	$ 363	$ 727