Description of Business	6 Months Ended
Description of Business	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Natural Gas Services Group, Inc. (the "Company", “NGS”, "Natural Gas Services Group", "we" or "our") (a Colorado corporation), is a leading provider of natural gas compression equipment and services to the energy industry. The Company manufactures, fabricates, rents, sells and maintains natural gas compressors and flare systems for oil and natural gas production and plant facilities. NGS is headquartered in Midland, Texas, with fabrication facilities located in Tulsa, Oklahoma and Midland, Texas, and service facilities located in major oil and natural gas producing basins in the U.S. Recent Events On January 30, 2020, the World Health Organization (“WHO”) announced a global health emergency because of a new strain of coronavirus known as COVID-19 due to the risks it imposes on the international community as the virus spreads globally. In March 2020, the WHO classified the COVID-19 outbreak as a pandemic, based on the rapid increase in exposure globally. The effects of the COVID-19 outbreak, including actions taken by businesses and governments to contain the spread of the virus, resulted in a significant, rapid decline in global and U.S. economic conditions. This significant drop in economic activity has caused global demand for crude oil to drastically decline. According to the International Energy Agency’s (“IEA”) Oil Market Report for July 2020, global crude oil demand during the second quarter of 2020 declined 16.4 million barrels per day (“MMbpd”) compared to the second quarter of 2019, a decrease of more than 15%. In March 2020, discussion between OPEC and Russia (“OPEC+”) resulted in Saudi Arabia significantly discounting the price of its crude oil, as well as Saudi Arabia and Russia significantly increasing their oil supply in April 2020. The dramatic decline in crude oil demand combined with this increase in supply resulted in unprecedented storage issues and a resulting severe lack of takeaway capacity for oil producers. As a result, crude oil prices reached record or multi-year lows in April. West Texas Intermediate (“WTI”) crude oil traded below $20 per barrel and Brent crude oil traded below $30 per barrel during the second half of April, including an anomalous trading day where WTI traded at negative values on low volume close to the end of a contract trading month. In April 2020, OPEC+ agreed to cut production by 9.7 MMbpd starting in May 2020, while Saudi Arabia voluntarily cut another 1 MMbpd starting in June 2020. Meanwhile, oil production dropped dramatically in non-OPEC countries, including the U.S. Burdened by low prices and takeaway issues, U.S. producers (including several of our customers) shut in production to varying degrees in April and May, and drilling and completion activities dramatically declined. According to IEA’s Oil Market Report for August 2020, U.S. production in May dropped 2 MMbpd from April and 2.9 MMbpd from its all-time high in November 2019. According to IEA’s July report, global oil supply fell to a nine-year low of 86.9 MMbpd in June. As states throughout the U.S., as well as many other countries around the world, began to lift restrictions and reopened their economies to varying degrees, global demand for crude oil partially recovered. This increased demand, combined with the production cuts mentioned above, have resulted in the oil markets coming back into balance. After trading below $20 per barrel in the second half of April and averaging $28.53 per barrel in May, WTI crude oil has averaged approximately $40 per barrel since June 1 with greatly reduced price volatility. These issues discussed above resulted in an increasing number of unit returns and shut-in notices from our customers during April and May 2020, which primarily impacted our small (125 HP or less) and medium (126 HP – 399 HP) horsepower units. In late May and throughout June as oil prices partially recovered and stabilized, we received restart notices for several wells that were recently shut in. As a result, our rental revenue, unit utilization, and horsepower utilization declined 6.0%, 5.2% and 4.5%, respectively, in the second quarter when compared to the first quarter of 2020. In addition, unit utilization remained steady in July compared to June, and unit pricing has stabilized. Nevertheless, risks remain high in this environment. As restrictions have been reduced in many states and countries, the rate of COVID-19 infections, hospitalizations and deaths has increased, particularly in the U.S. This has resulted in a reinstatement of some restrictions in several states, including Texas. If states and countries need to put further restrictions in place to help prevent the spread of the virus, crude oil demand could decline again. In addition, according to IEA’s August report, global oil supply rose by 2.5 MMbpd in July after Saudi Arabia ended its 1 MMbpd additional voluntary production cut and U.S. production increased. Additional shut-in production could be restored, and completion activities by domestic producers are likely to increase somewhat during the second half of 2020 to offset production declines. These risks to both supply and demand could negatively impact oil prices, which would impact our utilization, rental revenues and overall financial performance during the remainder of 2020 as well as 2021. Given the current economic and industry backdrop, we still expect compressor sales to be low for the remainder of 2020, as exploration and production companies have significantly reduced their capital expenditures budgets. In regards to our costs, we implemented various cost cutting measures with respect to operating expenses and capital expenditures during the second quarter. Our operating expense reductions included reductions in our headcount from both layoffs and attrition, wage freezes, centralization of certain processes for better cost control, and the enlistment of our suppliers in our cost cutting efforts. We expect these cost cutting measures to continue to benefit our financial performance through the remainder of 2020. In addition, as we have done during prior downturns, we have reduced our capital expenditures budget. We invested $11.0 million in capital expenditures during the first six months of 2020. After recently securing new rental orders from one of our larger customers, we plan to only incur another $8-$10 million in capital expenditures for the remainder of 2020, bringing our 2020 capital expenditures budget to $19-$21 million, down from $69.9 million in 2019. Finally, in keeping with current commercial precautions and practices in our industry, we implemented new guidelines to mitigate health risks to our employees and customers during this outbreak. We adopted remote and staggered work processes at our Midland headquarters. After reopening our headquarters in Midland, Texas on June 1, Midland experienced a significant increase in COVID-19 infections, including a verified positive test among the Company’s professional staff. As a result, the Company was forced to close its corporate headquarters for a second time on June 29, 2020. The Company’s corporate headquarters remains closed as of the date of this filing. The office closure - which was dictated by positive testing and subsequent quarantines - and staffing challenges resulted in delays in our collection and assimilation of financial data related to the completion of our interim financial statements required for this filing. With remote and staggered work processes back in place, we do not anticipate such issues going forward. In addition, we adapted our field and fabrication work processes as well. To date, our field operations have continued largely uninterrupted, as the U.S. Department of Homeland Security designated our industry as part of our country’s critical infrastructure. Remote work and work process adjustments related to COVID-19 have not impacted our ability to maintain of service operations or caused us to incur significant costs. In addition, we have not experienced any supply chain issues in connection with the COVID-19 outbreak. The full impact of the COVID-19 outbreak continues to evolve as of the date of this report. As such, it is uncertain as to the full magnitude that the pandemic will have on the Company's financial condition, liquidity, and future results of operations. Management is actively monitoring the global situation on its financial condition, liquidity, operations, suppliers, industry, and workforce. Given the daily evolution of the COVID-19 outbreak and the global responses to curb its spread, the Company is not able to estimate the effects of the COVID-19 outbreak on its results of operations, financial condition, or liquidity during the remainder of 2020 or 2021.