Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Foreign exchange rate used to translate amounts denominated in functional currency to reporting currency.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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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 uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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Credit Facilities - Outstanding Balance Under Credit Agreement (Details) € in Thousands, £ in Thousands, $ in Thousands	Sep. 30, 2019 EUR (€)	Sep. 30, 2019 $ / €	Sep. 30, 2019 USD ($)	Sep. 30, 2019 $ / £	Sep. 30, 2019 GBP (£)	Aug. 01, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 EUR (€)	Dec. 31, 2018 $ / €	Dec. 31, 2018 USD ($)	Dec. 31, 2018 $ / £	Dec. 31, 2018 GBP (£)
Line of Credit Facility [Line Items]
Revolving credit facility			$ 101,405							$ 363,894
Term Loan, Net			389,885							278,727
Foreign currency exchange rate (gbp, eur per usd)		1.09		1.23					1.14		1.27
Credit Facility \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility			101,400			$ 170,700	$ 259,500
KeyBank National Association \| Credit Facility \| Unsecured debt
Line of Credit Facility [Line Items]
Total Credit Facility			491,290							642,621
KeyBank National Association \| Credit Facility \| Unsecured debt \| USD
Line of Credit Facility [Line Items]
Total Credit Facility			52,211							278,625
KeyBank National Association \| Credit Facility \| Unsecured debt \| GBP
Line of Credit Facility [Line Items]
Total Credit Facility \| £					£ 40,000							£ 40,000
KeyBank National Association \| Credit Facility \| Unsecured debt \| EUR
Line of Credit Facility [Line Items]
Total Credit Facility \| €	€ 359,551							€ 276,481
KeyBank National Association \| Credit Facility \| Unsecured debt \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility			101,405							363,894
KeyBank National Association \| Credit Facility \| Unsecured debt \| Revolving Credit Facility \| USD
Line of Credit Facility [Line Items]
Revolving credit facility			52,211							278,625
KeyBank National Association \| Credit Facility \| Unsecured debt \| Revolving Credit Facility \| GBP
Line of Credit Facility [Line Items]
Revolving credit facility \| £					40,000							40,000
KeyBank National Association \| Credit Facility \| Unsecured debt \| Revolving Credit Facility \| EUR
Line of Credit Facility [Line Items]
Revolving credit facility \| €	0							30,000
KeyBank National Association \| Credit Facility \| Unsecured debt \| Term Facility
Line of Credit Facility [Line Items]
Term Loan			392,519							282,069
Deferred financing costs			(2,634)							(3,342)
Term Loan, Net			389,885							278,727
KeyBank National Association \| Credit Facility \| Unsecured debt \| Term Facility \| USD
Line of Credit Facility [Line Items]
Term Loan			0							0
Deferred financing costs			0							0
Term Loan, Net			$ 0							$ 0
KeyBank National Association \| Credit Facility \| Unsecured debt \| Term Facility \| GBP
Line of Credit Facility [Line Items]
Term Loan \| £					0							0
Deferred financing costs \| £					0							0
Term Loan, Net \| £					£ 0							£ 0
KeyBank National Association \| Credit Facility \| Unsecured debt \| Term Facility \| EUR
Line of Credit Facility [Line Items]
Term Loan \| €	359,551							246,481
Deferred financing costs \| €	0							0
Term Loan, Net \| €	€ 359,551							€ 246,481