Description of Business	12 Months Ended
Description of Business	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Mercury Systems, Inc. (the “Company” or “Mercury”) is a leading commercial provider of secure sensor and safety-critical mission processing subsystems. Headquartered in Andover, Massachusetts, the Company is delivering solutions that power a broad range of critical aerospace, defense and intelligence programs, configured and optimized for mission success in some of the most challenging and demanding environments. The Company's innovative next-generation defense electronics business model is designed to meet the industry’s current and emerging technology and business needs by delivering affordable state-of-the-art solutions, rapid time-to-value, service and support to the Company's defense prime contractor customers. The Company's products and solutions have been successfully deployed in more than 300 programs with over 25 different defense prime contractors, a testament to its deep domain expertise and culture of innovation. On May 20, 2019, the Company announced the commencement of an underwritten public offering of its common stock, par value $0.01 per share. On May 31, 2019 the Company closed the offering, including the full over-allotment allocation, selling an aggregate of 6,900 shares of common stock at a price to the public of $69.00 for total net proceeds of $454,343. On April 18, 2019, the Company acquired The Athena Group, Inc. (“Athena”) and Syntonic Microwave LLC (“Syntonic”) on a cash-free, debt-free basis for a combined total purchase price of $46,000, prior to net working capital and net debt adjustments. Athena was a privately-held company based in Gainesville, Florida and a leading provider of cryptographic and countermeasure IP vital to securing defense computing systems. Syntonic was a privately held company based in Campbell, California and a leading provider of advanced synthesizers, wideband phase coherent tuners and microwave converters optimized for signals intelligence and electronic intelligence applications demanding frequency coverage up to 40 GHz with 2 GHz instantaneous bandwidth. On January 29, 2019, the Company acquired GECO Avionics, LLC (“GECO”) on a cash-free, debt-free basis for a total purchase price of $36,500. Based in Mesa, Arizona, GECO has over twenty years of experience designing and manufacturing affordable safety-critical avionics and mission computing solutions. On July 31, 2018, the Company acquired Germane Systems, LC (“Germane”) on a cash-free, debt-free basis for a total purchase price of $45,000, prior to net working capital and net debt adjustments. Based in Chantilly, Virginia, Germane is an industry leader in the design, development and manufacturing of rugged servers, computers and storage systems for command, control and intelligence (“C2I”) applications. On February 1, 2018, the Company acquired Themis Computer (“Themis”) on a cash-free, debt-free basis for a total purchase price of approximately $180,000, prior to net working capital and net debt adjustments. Based in Fremont, California, Themis is a leading designer, manufacturer and integrator of commercial, SWaP-optimized rugged servers, computers and storage systems for U.S. and international defense programs. The acquisition of Themis is consistent with the Company's strategy and will expand its position in the Command, Control, Communications, Computers, and Intelligence (“C4I”) market. For further details on the acquisitions, see Note C to consolidated financial statements.