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Fair value of the amount outstanding under the credit facility.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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Amount, after tax, of reclassification from accumulated other comprehensive income (AOCI) of gain (loss) from increase (decrease) in fair value of net investment hedge.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Debt (Details) € in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
Debt (Details) € in Thousands, $ in Thousands	Sep. 30, 2019 USD ($) Rate	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) Rate	Sep. 30, 2018 USD ($)	Sep. 30, 2019 EUR (€) Rate
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 560,329		$ 560,329
Unamortized Debt Issuance Expense	(1,418)		(1,418)
Total debt	1,172,856		1,172,856
Debt, Current	48,577		48,577
Long-term Debt	1,124,279		1,124,279
Line of Credit Facility, Remaining Borrowing Capacity	529,200		529,200
Gain (Loss) on Derivative Used in Net Investment Hedge, after Tax	(5,300)	$ 1,800	(6,300)	$ (2,800)
Cumulative (gain) loss in other other comprehensive income related to the change in a net investment hedge.	(5,000)		(5,000)
Us Dollar Amounts Member
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	423,889		423,889
Unamortized Debt Issuance Expense	(1,111)		(1,111)
Total debt	909,963		909,963
Debt, Current	1,058		1,058
Long-term Debt	908,905		908,905
Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	136,440		136,440
Unamortized Debt Issuance Expense	(307)		(307)
Total debt	262,893		262,893
Debt, Current	47,519		47,519
Long-term Debt	$ 215,374		$ 215,374
1.30% Euro-Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	1.30%		1.30%		1.30%
Euro Notes - USD Amount	$ 149,900		$ 149,900
Debt Instrument, Maturity Date			Nov. 01, 2034
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 135,000		$ 135,000
Debt Instrument, Term			15 years
3.19% Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	3.19%		3.19%		3.19%
Debt Instrument, Maturity Date			Jan. 01, 2035
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 50,000		$ 50,000
Debt Instrument, Term			15 years
3.67% Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	3.67%		3.67%		3.67%
Debt Instrument, Maturity Date			Dec. 17, 2022
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 50,000		$ 50,000
3.67% Senior Notes [Member] \| Us Dollar Amounts Member
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	50,000		50,000
3.67% Senior Notes [Member] \| Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 0		$ 0
4.10% Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	4.10%		4.10%		4.10%
Debt Instrument, Maturity Date			Sep. 19, 2023
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 50,000		$ 50,000
4.10% Senior Notes [Member] \| Us Dollar Amounts Member
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	50,000		50,000
4.10% Senior Notes [Member] \| Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 0		$ 0
3.84% Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	3.84%		3.84%		3.84%
Debt Instrument, Maturity Date			Sep. 19, 2024
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 125,000		$ 125,000
3.84% Senior Notes [Member] \| Us Dollar Amounts Member
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	125,000		125,000
3.84% Senior Notes [Member] \| Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 0		$ 0
4.24% Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	4.24%		4.24%		4.24%
Debt Instrument, Maturity Date			Jun. 25, 2025
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 125,000		$ 125,000
4.24% Senior Notes [Member] \| Us Dollar Amounts Member
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	125,000		125,000
4.24% Senior Notes [Member] \| Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 0		$ 0
3.91% Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	3.91%		3.91%		3.91%
Debt Instrument, Maturity Date			Jun. 25, 2029
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 75,000		$ 75,000
3.91% Senior Notes [Member] \| Us Dollar Amounts Member
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	75,000		75,000
3.91% Senior Notes [Member] \| Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 0		$ 0
1.47% EURO Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	1.47%		1.47%		1.47%
Debt Instrument, Maturity Date			Jun. 17, 2030
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 136,747		$ 136,747		€ 125,000
1.47% EURO Senior Notes [Member] \| Us Dollar Amounts Member
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	0		0
1.47% EURO Senior Notes [Member] \| Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 136,747		$ 136,747
Credit facility [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage \| Rate	0.875%		0.875%		0.875%
Debt Instrument, Maturity Date			Jun. 15, 2023
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Senior Notes	$ 1,100,000		$ 1,100,000
Line of Credit Facility, Fair Value of Amount Outstanding	563,950		563,950
Credit facility [Member] \| Us Dollar Amounts Member
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Line of Credit Facility, Fair Value of Amount Outstanding	485,016		485,016
Credit facility [Member] \| Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Line of Credit Facility, Fair Value of Amount Outstanding	78,934		78,934
Other local arrangements [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Other Borrowings	48,577		48,577
Other local arrangements [Member] \| Us Dollar Amounts Member
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Other Borrowings	1,058		1,058
Other local arrangements [Member] \| Other Principal Trading Currencies [Member]
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Other Borrowings	$ 47,519		$ 47,519
Swiss Pension Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8750.00%		8750.00%		8750.00%
Long-Term Debt, by Current and Noncurrent, and Short-Term Debt
Loan from Swiss Pension Plan USD Amount	$ 39,600		$ 39,600
Swiss Pension Loans (local currency)	$ 38,000		$ 38,000