REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregate Revenue (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($) hp	Sep. 30, 2021 USD ($) hp	Sep. 30, 2022 USD ($) hp	Sep. 30, 2021 USD ($) hp
Disaggregation of Revenue
Revenue	$ 213,668	$ 195,166	$ 626,697	$ 586,212
Contract Operations
Disaggregation of Revenue
Revenue	170,497	158,911	500,451	488,810
Contract Operations | Transferred at Point in Time
Disaggregation of Revenue
Revenue	700	700	1,800	3,100
Contract Operations | 0 - 1,000 horsepower per unit
Disaggregation of Revenue
Revenue	$ 38,967	$ 41,576	$ 121,298	$ 134,413
Contract Operations | 0 - 1,000 horsepower per unit | Minimum
Disaggregation of Revenue
Compressor unit horsepower (horsepower) | hp	0	0	0	0
Contract Operations | 0 - 1,000 horsepower per unit | Maximum
Disaggregation of Revenue
Compressor unit horsepower (horsepower) | hp	1,000	1,000	1,000	1,000
Contract Operations | 1,001 - 1,500 horsepower per unit
Disaggregation of Revenue
Revenue	$ 72,463	$ 66,138	$ 208,161	$ 201,454
Contract Operations | 1,001 - 1,500 horsepower per unit | Minimum
Disaggregation of Revenue
Compressor unit horsepower (horsepower) | hp	1,001	1,001	1,001	1,001
Contract Operations | 1,001 - 1,500 horsepower per unit | Maximum
Disaggregation of Revenue
Compressor unit horsepower (horsepower) | hp	1,500	1,500	1,500	1,500
Contract Operations | Over 1,500 horsepower per unit
Disaggregation of Revenue
Revenue	$ 58,818	$ 51,018	$ 170,297	$ 152,360
Contract Operations | Over 1,500 horsepower per unit | Minimum
Disaggregation of Revenue
Compressor unit horsepower (horsepower) | hp	1,500	1,500	1,500	1,500
Contract Operations | Other
Disaggregation of Revenue
Revenue	$ 249	$ 179	$ 695	$ 583
Aftermarket Services
Disaggregation of Revenue
Revenue	43,171	36,255	126,246	97,402
Aftermarket Services | Services
Disaggregation of Revenue
Revenue	23,528	19,249	66,666	53,149
Aftermarket Services | Over-the-counter ("OTC") parts and components sales
Disaggregation of Revenue
Revenue	$ 19,643	$ 17,006	$ 59,580	$ 44,253