Borrowings (Details) € in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2020 EUR (€)	Dec. 31, 2019 USD ($)
Short-term borrowings [Abstract]
Commercial Paper	$ 90,500		$ 84,700
Notes payable and current maturities of long-term debt	90,500		84,700
Long-term borrowings [Abstract]
Net long-term debt	3,047,216		2,985,716
Unamortized debt discounts	17,800		18,900
Deferred debt issuance costs	14,800		16,200
Line of Credit Facility [Abstract]
Unsecured revolving credit facility, maximum borrowing capacity	$ 1,000,000
Line of Credit Facility, Covenant Compliance	The Company was in compliance with all covenants in the Credit Agreement, the Short-term Credit Agreement, and other long-term debt covenants at September 30, 2020 and had an interest coverage ratio of consolidated EBITDA to consolidated net interest expense of 11.0 to 1.
Letters of Credit Outstanding, Amount	$ 157,600
Current poriton of long-term debt and short-term borrowings	500,000
Line of Credit Facility, Current Borrowing Capacity	450,000
Note due 2025 [Member]
Long-term borrowings [Abstract]
Long-term debt	396,548		396,042
Debt Instrument, Face Amount	$ 400,000
Debt Instrument, Interest Rate, Stated Percentage	3.15%	3.15%
Line of Credit Facility [Abstract]
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Nov. 15, 2025
Note due 2026 [Member]
Long-term borrowings [Abstract]
Long-term debt	$ 690,939		658,089
Debt Instrument, Face Amount | €		€ 600,000
Debt Instrument, Interest Rate, Stated Percentage	1.25%	1.25%
Line of Credit Facility [Abstract]
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Nov. 09, 2026
Note due 2027 [Member]
Long-term borrowings [Abstract]
Long-term debt	$ 575,313		548,008
Debt Instrument, Face Amount | €		€ 500,000
Debt Instrument, Interest Rate, Stated Percentage	0.75%	0.75%
Line of Credit Facility [Abstract]
Debt Instrument, Term	8 years
Debt Instrument, Maturity Date	Nov. 04, 2027
Debentures due 2028 [Member]
Long-term borrowings [Abstract]
Long-term debt	$ 199,230		199,155
Debt Instrument, Face Amount	$ 200,000
Debt Instrument, Interest Rate, Stated Percentage	6.65%	6.65%
Line of Credit Facility [Abstract]
Debt Instrument, Term	30 years
Debt Instrument, Maturity Date	Jun. 01, 2028
Note due 2029
Long-term borrowings [Abstract]
Long-term debt	$ 296,555		296,270
Debt Instrument, Face Amount	$ 300,000
Debt Instrument, Interest Rate, Stated Percentage	2.95%	2.95%
Line of Credit Facility [Abstract]
Debt Instrument, Term	10 years
Debt Instrument, Maturity Date	Nov. 04, 2029
Debenture due 2035 [Member]
Long-term borrowings [Abstract]
Long-term debt	$ 296,247		296,060
Debt Instrument, Face Amount	$ 300,000
Debt Instrument, Interest Rate, Stated Percentage	5.375%	5.375%
Line of Credit Facility [Abstract]
Debt Instrument, Term	30 years
Debt Instrument, Maturity Date	Oct. 15, 2035
Note due 2038 [Member]
Long-term borrowings [Abstract]
Long-term debt	$ 248,024		247,939
Debt Instrument, Face Amount	$ 250,000
Debt Instrument, Interest Rate, Stated Percentage	6.60%	6.60%
Line of Credit Facility [Abstract]
Debt Instrument, Term	30 years
Debt Instrument, Maturity Date	Mar. 15, 2038
Note due 2041 [Member]
Long-term borrowings [Abstract]
Long-term debt	$ 344,360		$ 344,153
Debt Instrument, Face Amount	$ 350,000
Debt Instrument, Interest Rate, Stated Percentage	5.375%	5.375%
Line of Credit Facility [Abstract]
Debt Instrument, Term	30 years
Debt Instrument, Maturity Date	Mar. 01, 2041