Stockholders' Equity (Deficit) (Tables)

12 Months Ended

Dec. 31, 2020

Summary of Issued, Cancelled and Repurchased Shares of Common Stock

During the years ended December 31, the Company issued, cancelled and repurchased the following shares of common stock:     

	2020					2019				2018
	Shares			Average Price per Share		Shares		Average Price per Share		Shares			Average Price per Share
Common stock issued in connection    with initial public offering		11,500,000		$	15.00		—	$	—		—		$	—
Acquisitions		791,139			31.60		150,439		26.90		264,582			20.26
Redemption of series A-1 preferred stock		1,786,739			15.00		—		—		—			—
Exercise of warrant options		2,534,239			0.01		—		—		—			—
Exercise of options		47,600			8.06		27,350		6.16		5,000			6.03
Shares sold		—			—		42,415		31.60		—			—
Restricted shares, net		20,488			24.00		12,132		18.82		184,400			13.64
Cancellation of shares		(117,785	)		17.15		—		—		—			—
Repurchase of common shares		—			—		—		—		(277,714	)		9.80
Conversion of convertible preferred stock    into common stock		—			—		—		—		674,008			22.20
		16,562,420		$	13.72		232,336	$	24.89		850,276		$	30.10

Schedule of Share Authorized to be Issue and Available for Grant

The following number of shares were authorized to be issued and available for grant as of December 31:

	2017 Plan
	2020		2019		2018
Shares authorized to be issued		2,945,443		997,785		600,900
Shares available for grant		848,241		137,908		131,113
	2013 Plan
	2020		2019		2018
Shares authorized to be issued		2,047,269		2,058,619		2,154,600
Shares available for grant		—		1,550		79,946

Schedule of Stock Compensation Expense

Total stock compensation expense for the Plans was as follows:

	2020
	2017 plan				2013 plan
	Options		Restricted Stock		Options		Total
Cost of revenue	$	1,441	$	—	$	136	$	1,577
Selling, general and administrative expense		1,793		1,279		200		3,272
	$	3,234	$	1,279	$	336	$	4,849
	2019
	2017 plan				2013 plan
	Options		Restricted Stock		Options		Total
Cost of revenue	$	963	$	—	$	449	$	1,412
Selling, general and administrative expense		652		433		1,848		2,933
	$	1,615	$	433	$	2,297	$	4,345
	2018
	2017 plan				2013 plan
	Options		Restricted Stock		Options		Total
Cost of revenue	$	272	$	—	$	619	$	891
Selling, general and administrative expense		47		1,953		2,903		4,903
	$	319	$	1,953	$	3,522	$	5,794

Summary of Weighted Average Assumptions Used in Black-Sholes Option-pricing Model

The following weighted-average assumptions were used in the Black-Sholes option-pricing model calculation for the years ended December 31:

	2020			2019			2018
Common stock value (per share)	$	21.81		$	26.97		$	20.65
Expected volatility		46.59	%		48.13	%		48.69	%
Risk- free interest rate		0.65	%		2.06	%		2.88	%
Expected life (years)	7				7			7
Forfeiture rate	None			None			None
Dividend rate	None			None			None

Schedule of Common Stock Reserved for Future Issuance

Common Stock Reserved for Future Issuances—At December 31, 2020, 2019, and 2018, the Company has reserved certain stock of its authorized but unissued common stock for possible future issuance in connection with the following:

	2020		2019		2018
Warrants		116,350		650,590		650,590
Montrose 2013 Stock Incentive Plan		2,047,269		2,058,619		2,154,600
Montrose 2017 Stock Incentive Plan		2,945,443		997,785		600,900
Common stock reserved for future issuance		5,109,062		3,706,994		3,406,090

Montrose Amended & Restated 2017 Stock Incentive Plan

Summary of Stock Option Activity

 The following summarizes the options activity of the 2017 Plan for the years ended December 31:

	Options to Purchase Common Stock			Weighted-Average Exercise Price per Share		Weighted Average Grant Date Fair Value per Share		Weighted Average Remaining Contract Life (in Years)		Aggregate Intrinsic Value of In-The-Money Options (in Thousands)
Outstanding January 1, 2018		49,875		$	14	$	7		—	$	40
Granted		220,900			21		11		—		—
Forfeited/cancelled		(6,000	)		18		—		—		—
Expired		(7,013	)		14		—		—		—
Outstanding at December 31, 2018		257,762		$	20	$	10		—	$	1,151
Granted		380,820			27		14		—		—
Forfeited/cancelled		(20,730	)		20		—		—		—
Outstanding at December 31, 2019		617,852		$	24	$	12		7.82	$	4,696
Granted		1,243,027			22		12		—		—
Forfeited/cancelled		(17,225	)		22		—		—		—
Expired		(2,500	)		18		—		—		—
Exercised		(925	)		14		—		—		7,918
Outstanding at December 31, 2020		1,840,229		$	23	$	12		9.09	$	15,598
Exercisable at December 31, 2020		147,833			21		—		7.57		1,538
Options vested and expected to vest		1,840,229		$	23	$	—		9.09	$	15,598

Montrose Amended and Restated 2013 Stock Option Plan

Summary of Stock Option Activity

The following summarizes the activity of the 2013 Plan for the years ended December 31, 2020 and 2019:

				Weighted-		Weighted		Weighted		Aggregate
	Options to			Average		Average		Average		Intrinsic Value
	Purchase			Exercise		Grant Date		Remaining		of In-The- Money
	Common			Price per		Fair Value		Contract Life		Options
	Stock			Share		per Share		(in Years)		(in Thousands)
Outstanding January 1, 2018		2,066,000		$	6	$	1		7.83	$	16,534
Forfeited/cancelled		(43,225	)		7		—		—		—
Expired		(117,371	)		6		—		—		—
Exercised		(5,000	)		6		—		—		60
Outstanding at December 31, 2018		1,900,404		$	6	$	1		7.30	$	33,290
Forfeited/cancelled		(10,635	)		8		—		—		—
Expired		(6,950	)		8		—		—		—
Exercised		(27,350	)		6		—		—		—
Outstanding at December 31, 2019		1,855,469		$	6	$	1		6.40	$	46,617
Forfeited/cancelled		(7,500	)		10		—		—		—
Expired		(11,300	)		6		—		—		—
Exercised		(48,800	)		8		—		—		908
Outstanding at December 31, 2020		1,787,869		$	6	$	1		5.40	$	43,867
Exercisable at December 31, 2020		1,768,794			6		—		5.39		43,482
Options vested and expected to vest		1,787,869		$	6	$	—		5.40	$	43,867