Summary of Significant Accounting Policies (Details)					1 Months Ended		3 Months Ended								12 Months Ended
	Nov. 24, 2020 USD ($) $ / shares shares	Nov. 23, 2020 USD ($)	Nov. 19, 2020 USD ($) $ / shares shares	Nov. 12, 2020	May 31, 2020 shares	May 31, 2017 shares	Dec. 31, 2020 USD ($) $ / shares shares	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) Segment $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares
Initial Public Offering of Common Stock [Abstract]
Net proceeds from initial public offering															$ 272,813,000	$ 0	$ 0
Segment Reporting [Abstract]
Number of reportable segments | Segment															1
Number of operating segments | Segment															1
Revenue from Contract with Customer [Abstract]
Revenue recognized included in opening contract liabilities															$ 5,300,000	4,200,000	5,500,000
Disaggregation of Revenue [Abstract]
Revenue							$ 44,887,000	$ 47,440,000	$ 48,610,000	$ 38,980,000	$ 46,473,000	$ 45,531,000	$ 36,048,000	$ 31,166,000	179,917,000	159,218,000	138,016,000
Components of Contract Liabilities [Abstract]
Contract liabilities							5,700,000				6,300,000				5,700,000	6,300,000
Revenue, Performance Obligation [Abstract]
Remaining performance obligation							127,700,000				112,400,000				127,700,000	112,400,000
Inventories [Abstract]
Gross inventory							4,200,000				2,800,000				4,200,000	2,800,000
Allowance for Obsolescent Inventory [Roll Forward]
Balance beginning of year										$ 860,000				$ 520,000	860,000	520,000	1,484,000
Additions charge to costs and expense															(1,000)	376,000	30,000
Recoveries															(8,000)	(36,000)	(994,000)
Balance end of year							851,000				860,000				$ 851,000	860,000	520,000
Property and Equipment [Abstract]
Software development estimated useful life															2 years
Depreciation and amortization, including capital leases															$ 5,400,000	5,000,000	3,000,000
Research and Development [Abstract]
Capitalized software development costs							12,300,000				5,600,000				12,300,000	5,600,000
Amortization expense															1,700,000	1,800,000	$ 1,100,000
Accumulated amortization							$ 4,800,000				$ 3,100,000				$ 4,800,000	$ 3,100,000
Goodwill [Abstract]
Goodwill amortization period for income tax purposes															15 years
Restricted Stock Grants [Abstract]
Restricted stock remained subject to vesting (in shares) | shares							59,521								59,521
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount | shares															961	1,846
Exercise price per share of warrants (in dollars per share) | $ / shares							$ 1.665				$ 1.665				$ 1.665	$ 1.665
Reverse stock split				0.794
Comprehensive Income [Abstract]
Foreign currency translation															$ 63,000	$ 101,000
Gain on pension liability adjustment															$ 107,000	$ 107,000
Class A Common Stock [Member]
Class of Stock [Line Items]
Basic and diluted net loss per share (in dollars per share) | $ / shares																$ (0.17)	$ (0.04)
Basic and diluted weighted-average shares (in shares) | shares																34,525,000	33,558,000
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Reverse stock split															1.259446
Class B Common Stock [Member]
Class of Stock [Line Items]
Basic and diluted net loss per share (in dollars per share) | $ / shares																$ (0.17)	$ (0.04)
Basic and diluted weighted-average shares (in shares) | shares																3,204,000	3,204,000
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Reverse stock split															1.259446
Exchangeable Redeemable Preferred Stock [Member]
Initial Public Offering of Common Stock [Abstract]
Conversion of preferred stock to common stock		$ 108,900,000
ASC 606 [Member]
Revenue from Contract with Customer [Abstract]
Revenue accruals for multiple contracts as a result of cumulative indirect rate adjustments																	$ 6,000,000
Firm Fixed-Price [Member]
Disaggregation of Revenue [Abstract]
Revenue															$ 151,703,000	$ 131,629,000	103,454,000
Time-and-Materials [Member]
Disaggregation of Revenue [Abstract]
Revenue															13,455,000	14,569,000	16,795,000
Cost Plus Fixed Fee [Member]
Disaggregation of Revenue [Abstract]
Revenue															$ 14,759,000	13,020,000	17,767,000
Initial Public Offering [Member]
Initial Public Offering of Common Stock [Abstract]
Number of shares issued (in shares) | shares	17,200,000		17,200,000
Share price (in dollars per share) | $ / shares	$ 17.00		$ 17.00
Net proceeds from initial public offering	$ 272,800,000		$ 272,800,000
Repayment of senior term loan and subordinated debt	21,000,000		21,000,000
Initial Public Offering [Member] | Exchangeable Redeemable Preferred Stock [Member]
Initial Public Offering of Common Stock [Abstract]
Conversion of preferred stock to common stock	108,900,000		108,900,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Performance Obligation [Abstract]
Remaining performance obligation percentage							92.40%								92.40%
Remaining performance obligation, expected timing of satisfaction, period							1 year								1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Performance Obligation [Abstract]
Remaining performance obligation percentage							2.50%								2.50%
Remaining performance obligation, expected timing of satisfaction, period							2 years								2 years
Furniture and Equipment [Member] | Minimum [Member]
Property and Equipment [Abstract]
Software development estimated useful life															3 years
Furniture and Equipment [Member] | Maximum [Member]
Property and Equipment [Abstract]
Software development estimated useful life															5 years
Federal [Member]
Disaggregation of Revenue [Abstract]
Revenue															$ 171,677,000	149,257,000	129,279,000
State & Local, and Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue															$ 8,240,000	$ 9,961,000	$ 8,737,000
Telos ID [Member]
Business and Organization [Abstract]
Percentage of ownership							100.00%								100.00%
Telos ID [Member] | Initial Public Offering [Member] | Class B Common Stock [Member]
Initial Public Offering of Common Stock [Abstract]
Treasury stock repurchase	$ 30,000,000		$ 30,000,000
Unvested Restricted Stock [Member]
Restricted Stock Grants [Abstract]
Restricted stock issued during the period (in shares) | shares					79,361	3,972,007									79,361	0	0
Restricted stock vested on date of grant															25.00%
Restricted stock vest on anniversary of the date of grant															25.00%
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount | shares															60	945
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount | shares															901	901