Borrowings (Details) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2018 EUR (€)	Dec. 31, 2017 USD ($)
Letters of Credit [Abstract]
Letters of credit outstanding	$ 144,500
Maturities of Long-term Debt [Abstract]
2017	0
2018	340,369
2019	449,200
2020	0
2021	0
2022 and thereafter	2,154,091
Total future maturities	2,943,660
Debt Instrument [Line Items]
Short-term Debt	0		$ 350,402
Deferred Finance Costs, Own-share Lending Arrangement, Issuance Costs, Net	13,000		14,900
Short-term borrowings [Abstract]
Commercial paper	220,318		230,700
Total short-term debt	220,318		581,102
Long-term borrowings [Abstract]
Long-term Debt	2,943,660		3,336,713
Long-term Debt, Current Maturities	0		350,011
Total long-term debt	2,943,660		2,986,702
Unamortized discount	$ 15,800		17,600
Line of Credit Facility [Abstract]
Line of credit facility, interest rate description	At the Company's election, loans under the Credit Agreement will bear interest at a base rate plus an applicable margin.
Line of credit facility, covenant terms	the Credit Agreement requires the Company to pay a facility fee and imposes various restrictions on the Company such as, among other things, the requirement for the Company to maintain an interest coverage ratio of consolidated EBITDA to consolidated net interest expense of greater than or equal to 3.0 to 1
Line of credit facility, covenant compliance	9.6 to 1.0
Note due 2018 [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 0		349,918
Debt instrument, stated interest rate (in hundredths)	5.45%	5.45%
Debt Instrument, Term	10 years
Debt instruments, maturity date	Mar. 15, 2018
Face amount of notes	$ 350,000
Note due 2020 [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 339,657		354,349
Debt instrument, stated interest rate (in hundredths)	2.125%	2.125%
Debt Instrument, Term	7 years
Debt instruments, maturity date	Dec. 01, 2020
Face amount of notes | €		€ 300,000
Note due 2021 [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 449,200		448,831
Debt instrument, stated interest rate (in hundredths)	4.30%	4.30%
Debt Instrument, Term	10 years
Debt instruments, maturity date	Mar. 01, 2021
Face amount of notes	$ 450,000
Note due 2025 [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 395,368		394,695
Debt instrument, stated interest rate (in hundredths)	3.15%	3.15%
Debt Instrument, Term	10 years
Debt instruments, maturity date	Nov. 15, 2025
Face amount of notes	$ 400,000
Note due 2026 [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 672,103		701,058
Debt instrument, stated interest rate (in hundredths)	1.25%	1.25%
Debt Instrument, Term	10 years
Debt instruments, maturity date	Nov. 09, 2026
Face amount of notes | €		€ 600,000
Debentures due 2028 [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 199,054		198,954
Debt instrument, stated interest rate (in hundredths)	6.65%	6.65%
Debt Instrument, Term	30 years
Debt instruments, maturity date	Jun. 01, 2028
Face amount of notes	$ 200,000
Debenture due 2035 [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 295,811		295,561
Debt instrument, stated interest rate (in hundredths)	5.375%	5.375%
Debt Instrument, Term	30 years
Debt instruments, maturity date	Oct. 15, 2035
Face amount of notes	$ 300,000
Note due 2038 [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 247,827		247,713
Debt instrument, stated interest rate (in hundredths)	6.60%	6.60%
Debt Instrument, Term	30 years
Debt instruments, maturity date	Mar. 15, 2038
Face amount of notes	$ 250,000
Note due 2041 [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 343,877		343,600
Debt instrument, stated interest rate (in hundredths)	5.375%	5.375%
Debt Instrument, Term	30 years
Debt instruments, maturity date	Mar. 01, 2041
Face amount of notes	$ 350,000
Other long term debt instruments [Member]
Long-term borrowings [Abstract]
Long-term Debt	$ 763		$ 2,034