Debt - Components of Debt (Details) - USD ($) $ in Thousands	6 Months Ended		18 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017
Components of beginning debt balance [Abstract]
Long term debt, current portion, net of deferred issuance cost at beginning of period	$ 8,410
Long term debt, net of deferred issuance cost at beginning of period	245,731
Debt Borrowing, Repayment, Amortization during period [Abstract]
Repayment of debt and revolving credit facility	(70,500)	$ (22,500)
Amortization of deferred issuance cost	795	$ 795
Components of ending debt balance [Abstract]
Long term debt, current portion, net of deferred issuance cost at end of period	10,910		$ 10,910
Long term debt, net of deferred issuance cost at end of period	183,526		183,526
Wells Fargo Bank, National Association
Components of beginning debt balance [Abstract]
Debt under credit facilities at beginning of period	260,500
Deferred issuance cost, net at beginning of period	(6,359)
Total Debt, net of deferred issuance cost at beginning of period	254,141
Long term debt, current portion, net of deferred issuance cost at beginning of period	8,410
Long term debt, net of deferred issuance cost at beginning of period	245,731
Debt Borrowing, Repayment, Amortization during period [Abstract]
Proceeds from lines of credit	10,000
Deferred issuance cost, gross	0
Increase in borrowings net of deferred issuance cost	10,000
Repayment of debt and revolving credit facility	(70,500)		(105,000)
Amortization of deferred issuance cost	795
Decrease in repayment/amortization net of deferred issuance cost	(69,705)
Components of ending debt balance [Abstract]
Debt under credit facilities at end of period	200,000		200,000
Deferred issuance cost, net at end of period	(5,564)		(5,564)
Total Debt, net of deferred issuance cost at end of period	194,436		194,436
Long term debt, current portion, net of deferred issuance cost at end of period	10,910		10,910
Long term debt, net of deferred issuance cost at end of period	183,526		183,526
Wells Fargo Bank, National Association | Term Loan Facility
Components of beginning debt balance [Abstract]
Debt under credit facilities at beginning of period	192,500
Debt Borrowing, Repayment, Amortization during period [Abstract]
Proceeds from lines of credit	0
Repayment of debt and revolving credit facility	(5,000)
Components of ending debt balance [Abstract]
Debt under credit facilities at end of period	187,500		187,500
Wells Fargo Bank, National Association | Revolving Credit Facility
Components of beginning debt balance [Abstract]
Debt under credit facilities at beginning of period	68,000
Debt Borrowing, Repayment, Amortization during period [Abstract]
Proceeds from lines of credit	10,000
Repayment of debt and revolving credit facility	(65,500)
Components of ending debt balance [Abstract]
Debt under credit facilities at end of period	$ 12,500		$ 12,500