Stockholders' Equity (Deficit) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2020

Dec. 31, 2019

Summary of Issued and Cancelled Shares of Common Stock

Common Stock Issuances and Cancellations—During the three and nine months ended September 30, 2020 and September 30, 2019, the Company issued and cancelled the following shares of common stock:

	Three Months Ended September 30,									Nine Months Ended September 30,
	2020					2019				2020					2019
	Shares			Average Price per Share		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		—	$	—		11,500,000		$	15.00		—	$	—
Acquisitions		—			—		25,408		26.90		791,139			31.60		150,439		22.41
Redemption of series A-1 preferred stock		1,786,739			15.00		—		—		1,786,739			15.00		—		—
Exercise of warrant options		2,534,239			0.01		—		—		2,534,239			0.01		—		—
Exercise of options		16,850			8.92		7,150		6.03		20,350			9.27		22,675		18.01
Restricted shares, net		8,333			24.00		—		—		8,333			24.00		—		—
Cancellation of shares		(117,785	)		17.15		—		—		(117,785	)		17.15		—		—
		15,728,376		$	12.82		32,558	$	22.32		16,523,015		$	13.72		173,114	$	21.83

Common Stock Issuances and Repurchases—During the years ended December 31, 2019 and 2018, the Company issued common stock in connection with (i) business acquisitions, (ii) as part of the exercise of options by certain participants, (iii) as part of a common stock offering to certain employees, (iv) through the conversion of the convertible preferred stock into common stock and (v) the vesting of restricted stock. Details of common stock issuances are as follows:

2019	Number of Shares		Average Price per Share
Acquisitions		150,439	$	26.90
Exercise of options		27,350		6.16
Shares sold		42,415		31.60
Release of restricted stock		12,132		18.82
		232,336

2018	Number of Shares		Average Price per Share
Acquisitions		264,582	$	20.26
Exercise of options		5,000		6.03
Release of restricted stock		184,400		13.64
		453,982

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 September 30, 2020 and September 30, 2019:

	September 30, 2020
	2017 Plan		2013 Plan
Shares authorized to be issued		2,945,443		2,047,269
Shares available for grant		1,233,266		—
	September 30, 2019
	2017 Plan		2013 Plan
Shares authorized to be issued		981,800		2,074,604
Shares available for grant		159,428		—

Schedule of Stock Compensation Expense

Total stock compensation expense for the Plans was as follows:

	Three Months Ended September 30,
	2020									2019
	2017 plan				2013 plan					2017 plan				2013 plan
	Options		Restricted Stock		Options			Total		Options		Restricted Stock		Options		Total
Cost of revenue	$	276	$	—	$	(5	)	$	271	$	278	$	—	$	97	$	375
Selling, general and administrative expense		592		233		53			878		185		111		384		680
	$	868	$	233	$	48		$	1,149	$	463	$	111	$	481	$	1,055

	Nine Months Ended September 30,
	2020								2019
	2017 plan				2013 plan				2017 plan				2013 plan
	Options		Restricted Stock		Options		Total		Options		Restricted Stock		Options		Total
Cost of revenue	$	973	$	—	$	126	$	1,099	$	623	$	—	$	390	$	1,013
Selling, general and administrative expense		1,178		973		189		2,340		457		323		1,784		2,564
	$	2,151	$	973	$	315	$	3,439	$	1,080	$	323	$	2,174	$	3,577

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 nine months ended September 30, 2020 and September 30, 2019:

	September 30, 2020		September 30, 2019
Common stock value (per share)	$	16.36	$	27.30
Expected volatility		46.14		47.94
Risk-free interest rate		0.41		2.15
Expected life (years)		7		7
Forfeiture rate		None		None
Dividend rate		None		None

The following weighted-average assumptions were used in the Black-Sholes option-pricing model calculation for the years ended December 31, 2019 and 2018:

	2019	2018
Common stock value (per share)	$24.00–$31.60	$18.00–$24.00
Expected volatility	48.13%	48.69%
Risk- free interest rate	1.43%–2.63%	2.86%–2.89%
Expected life (years)	7.00	7.00
Forfeiture rate	None	None
Dividend rate	None	None

Schedule of Common Stock Reserved for Future Issuance

Common Stock Reserved for Future Issuances—At September 30, 2020 and September 30, 2019, the Company has reserved certain stock of its authorized but unissued common stock for possible future issuance in connection with the following:

	September 30, 2020		December 31, 2019
Warrants		116,350		650,590
Montrose 2013 Stock Incentive Plan		2,047,269		2,058,619
Montrose 2017 Stock Incentive Plan		2,945,443		997,785
Common stock reserved for future issuance		5,109,062		3,706,994

Common Stock Reserved for Future Issuances—At December 31, 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:

	2019		2018
Warrants		650,590		650,590
Montrose 2013 Stock Incentive Plan		2,058,619		2,154,600
Montrose 2017 Stock Incentive Plan		997,785		600,900
Common stock reserved for future issuance		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 nine months ended September 30, 2020 and September 30, 2019:

	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 at December 31, 2018		257,762		$	20	$	10		—	$	1,151
Granted		356,470			27		14		—		—
Forfeited/ cancelled		(17,700	)		19		—		—		—
Outstanding at September 30, 2019		596,532			24		12		8.07		4,693
Outstanding at December 31, 2019		617,852			24		12		7.82		4,693
Granted		851,877			32		12		—		—
Forfeited/ cancelled		(14,375	)		22		—		—		—
Exercised		(925	)		14		—		—		7,918
Outstanding at September 30, 2020		1,454,429			21		12		7.59		7,649
Exercised at September 30, 2020		925			14		—		7.33		7,649
Options vested and expected to vest		1,454,429			21				9.04		7,649

The following summarizes the options activity of the 2017 Stock Incentive Plan for the years ended December 31, 2019 and 2018:

				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 at January 1, 2018		49,875		$	14	$	7			$	40
Granted		220,900			21		11
Forfeitured/cancelled		(6,000	)		18
Expired		(7,013	)		14
Outstanding at December 31, 2018		257,762			20		10				1,151
Granted		380,820			27		14
Forfeitured/cancelled		(20,730	)		20
Outstanding at December 31, 2019		617,852			24		12		7.82		4,696
Options vested and expected to vest		617,852			24				8.79		4,696

Montrose Amended and Restated 2013 Stock Option Plan

Summary of Stock Option Activity

Montrose Amended & Restated 2013 Stock Option Plan—The following summarizes the activity of the 2013 Plan for the nine months ended September 30, 2020 and September 30, 2019:

	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 at December 31, 2018		1,900,404		$	6	$	1		7.30		33,290
Forfeited/ cancelled		(14,500	)		8		—		—		—
Expired		(5,400	)		8		—		—		—
Exercised		(19,010	)		6		—		—		466
Outstanding at September 30, 2019		1,861,494			6		1		6.65		47,381
Outstanding at December 31, 2019		1,855,469			6		1		6.40		46,617
Forfeited/ cancelled		(7,500	)		10		—		—		—
Expired		(11,300	)		6		—		—		—
Exercised		(19,175	)		8		—		—		354
Outstanding at September 30, 2020		1,817,494			6		1		5.63		33,772
Exercised at September 30, 2020		221,025			6		—		5.14		33,772
Options vested and expected to vest		1,817,494			6		—		5.17		33,772

The following summarizes the activity of the Montrose Amended & Restated 2013 Stock Option Plan for the years ended December 31, 2019 and 2018:

				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 at January 1, 2018		2,066,000		$	6	$	1		7.83	$	16,534
Forfeitured/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
Forfeitured/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
Exercised at December 31, 2019		201,600			6				5.90		46,617
Options vested and expected to vest		1,855,494			6				5.86		46,617