Borrowings (Details) € in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 EUR (€)	Dec. 31, 2018 USD ($)
Short-term borrowings [Abstract]
Commercial Paper	$ 357,700		$ 220,318
Notes payable and current maturities of long-term debt	357,700		220,318
Long-term borrowings [Abstract]
Net long-term debt	2,946,493		2,943,660
Unamortized debt discounts	15,100		15,800
Deferred debt issuance costs	12,100		13,000
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 and other long-term debt covenants at June 30, 2019 and had an interest coverage ratio of consolidated EBITDA to consolidated net interest expense of 10.0 to 1.0.
Letters of Credit Outstanding, Amount	$ 142,100
Note due 2020 [Member]
Long-term borrowings [Abstract]
Long-term debt	340,285		339,657
Debt Instrument, Face Amount | €		€ 300,000
Note due 2021 [Member]
Long-term borrowings [Abstract]
Long-term debt	449,385		449,200
Debt Instrument, Face Amount	450,000
Note due 2025 [Member]
Long-term borrowings [Abstract]
Long-term debt	395,705		395,368
Debt Instrument, Face Amount	400,000
Note due 2026 [Member]
Long-term borrowings [Abstract]
Long-term debt	673,448		672,103
Debt Instrument, Face Amount | €		€ 600,000
Debentures due 2028 [Member]
Long-term borrowings [Abstract]
Long-term debt	199,105		199,054
Debt Instrument, Face Amount	200,000
Debenture due 2035 [Member]
Long-term borrowings [Abstract]
Long-term debt	295,935		295,811
Debt Instrument, Face Amount	300,000
Note due 2038 [Member]
Long-term borrowings [Abstract]
Long-term debt	247,883		247,827
Debt Instrument, Face Amount	250,000
Note due 2041 [Member]
Long-term borrowings [Abstract]
Long-term debt	344,015		343,877
Debt Instrument, Face Amount	350,000
Other long term debt instruments [Member]
Long-term borrowings [Abstract]
Long-term debt	$ 732		$ 763