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Long-Term Debt (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 01, 2016
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net				$ 3,689	$ 3,052
Long-term Debt				660,863	421,948
Long-term debt, current portion				12,444	0
Long-term Debt, Excluding Current Maturities				648,419	421,948
Credit Agreement
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 239,552	0
Term of agreement				5 years
3.75 % senior unsecured notes due September 1, 2016
Debt Instrument [Line Items]
Term of agreement				5 years
Three Point One Two Five Percent Senior Unsecured Notes Due June Fifteenth Twenty Twenty Five [Domain]
Debt Instrument [Line Items]
Senior unsecured notes, issued amount							$ 425,000
Senior unsecured notes, interest rate						3.125%
Senior unsecured notes, proceeds		$ 421,000
Term of agreement	5 years
Term loan facility [Member]
Debt Instrument [Line Items]
Proceeds from Debt, Net of Issuance Costs			$ 100,000
Unsecured notes
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 425,000	$ 425,000
Revolving Credit Facility
Debt Instrument [Line Items]
Proceeds from Debt, Net of Issuance Costs				$ 100,000