Debt and Credit Agreements - Components of Debt (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Debt Borrowing, Repayment, Amortization during period [Abstract]
Repayment of debt and revolving credit facility	$ (39,000)	$ (2,500)
Amortization of deferred issuance cost	573	$ 573
Wells Fargo Bank, National Association
Components of beginning debt balance [Abstract]
Debt under credit facilities at beginning of period	140,000
Deferred issuance cost, net at beginning of period	(4,583)
Total Debt, net of deferred issuance cost at beginning of period	135,417
Debt Borrowing, Repayment, Amortization during period [Abstract]
Proceeds from lines of credit	0
Deferred issuance cost, gross	0
Increase in borrowings net of deferred issuance cost	0
Repayment of debt and revolving credit facility	(39,000)
Amortization of deferred issuance cost	573
Decrease in repayment/amortization net of deferred issuance cost	(38,427)
Components of ending debt balance [Abstract]
Debt under credit facilities at end of period	101,000
Deferred issuance cost, net at end of period	(4,010)
Total Debt, net of deferred issuance cost at end of period	96,990
Wells Fargo Bank, National Association | Term loan facility
Components of beginning debt balance [Abstract]
Debt under credit facilities at beginning of period	140,000
Debt Borrowing, Repayment, Amortization during period [Abstract]
Proceeds from lines of credit	0
Repayment of debt and revolving credit facility	(39,000)
Components of ending debt balance [Abstract]
Debt under credit facilities at end of period	101,000
Wells Fargo Bank, National Association | Revolving credit facility
Components of beginning debt balance [Abstract]
Debt under credit facilities at beginning of period	0
Debt Borrowing, Repayment, Amortization during period [Abstract]
Proceeds from lines of credit	0
Repayment of debt and revolving credit facility	0
Components of ending debt balance [Abstract]
Debt under credit facilities at end of period	$ 0