Revolving Credit Facility and Long-Term Debt - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Outstanding borrowings	$ 440,500
Collateralized debt facility		$ 7,000
Term Loan
Line of Credit Facility [Line Items]
Outstanding borrowings	150,000	72,500
Revolving Credit Facility
Line of Credit Facility [Line Items]
Outstanding borrowings	290,500	$ 316,000
Credit Agreement
Line of Credit Facility [Line Items]
Outstanding borrowings	440,500
Remaining borrowing capacity on line of credit	$ 191,100
Fixed interest rate percent	2.37%	2.12%
Debt subject to fixed interest rate	$ 175,000	$ 175,000
Variable interest rate percent	3.29%	3.52%
Debt subject to variable interest rate	$ 265,500	$ 213,500
Credit Agreement | Term Loan
Line of Credit Facility [Line Items]
Debt instrument, face amount	150,000
Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 600,000