Consolidated leverage ratio per debt agreement. It is defined as, with certain adjustments, the ratio of the Company's consolidated indebtedness to consolidated net income before interest, taxes, depreciation, amortization, non-cash charges and certain other items ("EBITDA")).

No definition available.

LONG TERM DEBT - Credit Agreement (Details) $ in Thousands								12 Months Ended
LONG TERM DEBT - Credit Agreement (Details) $ in Thousands	Sep. 30, 2017	Jun. 23, 2017	Sep. 30, 2016	Jul. 15, 2016	Sep. 30, 2015	Sep. 30, 2014	Jun. 17, 2013 USD ($)	Dec. 31, 2017 USD ($) agreement	Dec. 31, 2016 USD ($) agreement	Dec. 31, 2015 USD ($)
Long-Term Debt
Final amount due in 2018								$ 161,382
Federal income tax refunds								$ 34,100
Percentage tax refunds to be applied to reduce revolving commitments								50.00%
Credit Agreement
Long-Term Debt
Term of agreement							5 years
Maximum borrowing capacity							$ 425,000
Number of agreements entered into \| agreement								3	3
Minimum commitment as a result of tax refunds								$ 108,000
Maximum leverage ratio to use maximum credit facility								4.00
Interest rate margin (as a percent)								7.32%	5.52%	2.43%
Increase in interest rate in case of failure to deliver audited financial statements (as a percent)									2.00%	2.00%
Credit Agreement \| Last day of the fiscal quarter ending June 30, 2016
Long-Term Debt
Consolidated leverage ratio		5.00%
Interest coverage ratio (as a percent)		3.50
Credit Agreement \| Last day of the fiscal quarter ending September 30, 2016
Long-Term Debt
Consolidated leverage ratio		5.75%
Credit Agreement \| Last day of each fiscal quarter after September 30, 2016
Long-Term Debt
Consolidated leverage ratio		5.00%
Credit Agreement \| LIBOR
Long-Term Debt
Interest rate margin (as a percent)								5.75%
Interest rate margin contingent on delivery of financial information and leverage ratio of 4.00 to 1.00								4.00%
Credit Agreement \| Base rate
Long-Term Debt
Interest rate margin contingent on delivery of financial information and leverage ratio of 4.00 to 1.00								3.00%
Credit Agreement \| Federal funds rate
Long-Term Debt
Interest rate margin (as a percent)								0.50%
Credit Agreement \| One-month LIBOR
Long-Term Debt
Interest rate margin (as a percent)								4.75%
Fixed interest rate of debt (as a percent)								1.00%
Revolving Credit Facility \| Credit Agreement
Long-Term Debt
Maximum borrowing capacity							200,000
Available credit facility								$ 118,300
Letters of credit outstanding amount								$ 6,200	$ 6,100
Unused commitment fee (as a percent)								0.375
Unused commitment fee								$ 400	300	$ 200
Balance available under the credit facility								86,400	$ 94,900
Revolving Credit Facility \| Credit Agreement \| From July 15, 2016 to September 30, 2016
Long-Term Debt
Reduction of the available credit facility depending on fiscal quarter results								13,900
Revolving Credit Facility \| Credit Agreement \| Three month period ending December 31, 2016
Long-Term Debt
Reduction of the available credit facility depending on fiscal quarter results								17,300
Revolving Credit Facility \| Credit Agreement \| Three month period ending March 31, 2017
Long-Term Debt
Reduction of the available credit facility depending on fiscal quarter results								10,700
Revolving Credit Facility \| Credit Agreement \| Nine month period ending December 31, 2017
Long-Term Debt
Reduction of the available credit facility depending on fiscal quarter results								20,700
Revolving Credit Facility \| Credit Agreement \| Three months period ending March 31, 2018
Long-Term Debt
Reduction of the available credit facility depending on fiscal quarter results								10,700
Revolving Credit Facility \| Credit Agreement \| Periods subsequent to March 31, 2018
Long-Term Debt
Available credit facility								20,700
Term Loan \| Credit Agreement
Long-Term Debt
Maximum borrowing capacity							225,000
Available credit facility								225,000
Initial amount borrowed							$ 225,000
Quarterly principal payments, as a percent to initial amount borrowed	3.75%		2.50%		1.875%	1.25%	0.625%
Final amount due in 2018								$ 143,400
Interest rate in excess of applicable rate upon acceleration and default ( as a percent)				2.00%