ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) - Schedule of Amounts Reclassified From AOCI By Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax Effect	$ (346,186)	$ (273,499)	$ (288,972)
Net Income Attributable to Common Shareholders	1,205,167	909,053	1,033,000
Defined Benefit Plan Costs:
Total Amounts Reclassified from AOCI, Net of Tax	(7,900)	(7,000)	(6,600)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax Effect	900	1,100	1,000
Qualified Cash Flow Hedging Instruments, Net of Tax | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income Attributable to Common Shareholders	(1,600)	(1,400)	(1,800)
Amortization of Actuarial Losses
Defined Benefit Plan Costs:
Reclassifications from AOCI	(8,100)	(5,700)	(6,000)
Amortization of Prior Service Cost
Defined Benefit Plan Costs:
Reclassifications from AOCI	(300)	(1,800)	(400)
Defined Benefit Plans
Defined Benefit Plan Costs:
Reclassifications from AOCI	(8,400)	(7,500)	(6,400)
Tax Effect	2,100	1,900	1,600
Total Amounts Reclassified from AOCI, Net of Tax	(6,300)	(5,600)	(4,800)
Interest Expense | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Qualified Cash Flow Hedging Instruments	$ (2,500)	$ (2,500)	$ (2,800)