LONG-TERM DEBT - Line of Credit and Senior Term Loan (Details) - USD ($)							1 Months Ended	3 Months Ended	6 Months Ended
	Jun. 15, 2018	Nov. 28, 2017	Aug. 31, 2017	Aug. 16, 2017	Aug. 15, 2017	Feb. 27, 2017	Apr. 30, 2016	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017
LONG-TERM DEBT
Proceeds from Term Loan Facility										$ 289,500,000
Senior Debt
LONG-TERM DEBT
Credit facility						$ 350,000,000
Senior term loan
LONG-TERM DEBT
Fixed charge coverage ratio Trailing Period									12 months
Real estate term loan
LONG-TERM DEBT
Monthly installments									$ 59,109
Term loan amortization period									20 years
Loan amount							$ 14,200,000
Real estate term loan | LIBOR
LONG-TERM DEBT
Basis spread on variable rate							2.75%
Term loan facility
LONG-TERM DEBT
Credit facility						$ 250,000,000
Term loan facility | Credit Suisse AG
LONG-TERM DEBT
Percentage of EBITDA permitted to be added back (as a percent)									25.00%
Repayment of term loan (in percentage)									50.00%
Percentage of excess cash flow, mandatory prepayment, 2018									50.00%
Percentage of excess cash flow, mandatory prepayment, 2019									25.00%
Percentage of excess cash flow, mandatory prepayment, 2020									0.00%
Term loan facility | Credit Suisse AG | Commencing March 31 2018
LONG-TERM DEBT
Consolidated total leverage ratio commencing on March 31, 2018									4.25%
Term loan facility | Credit Suisse AG | Commencing March 31 2019
LONG-TERM DEBT
Consolidated total leverage ratio commencing on March 31, 2019									4.00%
Term loan facility | Credit Suisse AG | Commencing March 31 2021
LONG-TERM DEBT
Consolidated total leverage ratio commencing on March 31, 2021									3.75%
Term loan facility | Credit Suisse AG | Base Rate
LONG-TERM DEBT
Floor rate (as a percent)						2.00%
Basis spread on variable rate		4.00%				4.50%
Term loan facility | Credit Suisse AG | LIBOR
LONG-TERM DEBT
Floor rate (as a percent)						1.00%
Basis spread on variable rate		5.00%				5.50%
Term loan facility | Senior Debt | Credit Suisse AG
LONG-TERM DEBT
Credit facility						$ 350,000,000
Average interest rate on term loan									6.80%
Term loan facility | Senior term loan | Credit Suisse AG
LONG-TERM DEBT
Credit facility						250,000,000
Uncommitted Incremental Facility | Senior Debt | Credit Suisse AG
LONG-TERM DEBT
Committed amount						65,000,000
Tack-on Loan
LONG-TERM DEBT
Credit facility		$ 150,000,000
ABL Member
LONG-TERM DEBT
Credit facility						70,000,000
Availability at closing								$ 82,400,000	$ 82,400,000
Excess availability falling below amount			$ 15,000,000
Maximum credit amount (as a percent)			20.00%
Number of consecutive days, a financial covenant requiring the Company to maintain a minimum consolidated fixed charge coverage ratio			60 days
Minimum consolidated fixed charge coverage ratio			1.00%
ABL Member | Commencing March 31 2018
LONG-TERM DEBT
Consolidated total leverage ratio commencing on March 31, 2018								4.25%
ABL Member | Commencing March 31 2021
LONG-TERM DEBT
Consolidated total leverage ratio commencing on March 31, 2021								3.75%
ABL Member | PNC Bank National Association
LONG-TERM DEBT
Credit facility	$ 100,000,000					$ 70,000,000
Term loan amortization period						5 years
Percentage of accounts receivable used as part of the borrowing base calculation						85.00%
Percentage of unbilled accounts receivable used as part of the borrowing base calculation						80.00%
Percentage of parts supplies used as part of the borrowing base calculation						50.00%
Line Of Credit Facility, Maximum	$ 30,000,000
Line of credit sublimit						$ 20,000,000
Outstanding letters of credit								$ 200,000	200,000
ABL Member | Letter of credit
LONG-TERM DEBT
Outstanding letters of credit								$ 8,700,000	$ 8,700,000
Revolving credit facility | PNC Bank National Association | Base Rate | Less than 1.25 to 1.00
LONG-TERM DEBT
Fixed charge coverage ratio									2.25%
Revolving credit facility | PNC Bank National Association | Base Rate | Greater than or equal to 1.25 to 1.00, but less than 1.50 to 1.00
LONG-TERM DEBT
Fixed charge coverage ratio									1.75%
Revolving credit facility | PNC Bank National Association | Base Rate | Greater than or equal to 1.50 to 1.00, but less than 1.75
LONG-TERM DEBT
Fixed charge coverage ratio									1.25%
Revolving credit facility | PNC Bank National Association | Base Rate | Greater than or equal to 1.75 to 1.00
LONG-TERM DEBT
Fixed charge coverage ratio									0.75%
Revolving credit facility | PNC Bank National Association | LIBOR | Less than 1.25 to 1.00
LONG-TERM DEBT
Fixed charge coverage ratio									3.25%
Revolving credit facility | PNC Bank National Association | LIBOR | Greater than or equal to 1.25 to 1.00, but less than 1.50 to 1.00
LONG-TERM DEBT
Fixed charge coverage ratio									2.75%
Revolving credit facility | PNC Bank National Association | LIBOR | Greater than or equal to 1.50 to 1.00, but less than 1.75
LONG-TERM DEBT
Fixed charge coverage ratio									2.25%
Revolving credit facility | PNC Bank National Association | LIBOR | Greater than or equal to 1.75 to 1.00
LONG-TERM DEBT
Fixed charge coverage ratio									1.75%
Delayed Draw Feature
LONG-TERM DEBT
Credit facility						100,000,000
Delayed Draw Feature | Credit Suisse AG
LONG-TERM DEBT
Leverage ratio									4.25%
Delayed Draw Feature | Senior Debt | Credit Suisse AG
LONG-TERM DEBT
Credit facility						$ 100,000,000
Leverage ratio				4.25%	3.50%
Proceeds from Term Loan Facility				$ 60,500,000