Stockholders' Equity - Additional Information (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Mar. 29, 2022 USD ($) $ / shares shares	Mar. 31, 2021 USD ($) $ / shares shares	Mar. 31, 2022 USD ($) Vote $ / shares shares	Mar. 28, 2022 $ / shares shares	Mar. 09, 2022 shares	Dec. 31, 2021 $ / shares shares
Class Of Stock [Line Items]
Preferred stock, shares authorized			10,000,000
Preferred stock, shares issued			0
Conversion of preferred stock terms			each share of Series Z Preferred Stock automatically converted into Class A common stock on a one-to-one basis
Preferred stock, par value | $ / shares			$ 0.0001
Preferred stock, shares outstanding			0
Recognition of distribution to non-redeeming shareholders | $			$ 3,888
2020 Convertible Notes
Class Of Stock [Line Items]
Carrying value | $		$ 31,752
2021 Convertible Notes
Class Of Stock [Line Items]
Carrying value | $		$ 13,832
Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized			0
Preferred stock, shares issued			0
Preferred stock, shares outstanding			0
Series Z Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares issued	4,133,333
Purchase price | $ / shares	$ 7.50
Gross cash proceeds | $	$ 31,000
Conversion of preferred stock terms			shares of Series Z Preferred Stock converted into shares of Class A common stock on a 1-for-1 basis
Series E-1 Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares issued upon conversion		22,204,490
Preferred stock, conversion price | $ / shares		$ 1.43
Series E-2 Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares issued upon conversion		8,232,627
Preferred stock, conversion price | $ / shares		$ 1.34
Series E-3 Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares issued		71,428,570
Purchase price | $ / shares		$ 1.68
Gross cash proceeds | $		$ 120,000
Issuance cost | $		$ 150
Class A Common Stock
Class Of Stock [Line Items]
Conversion of preferred stock ratio			0.1841
Common stock, shares authorized			800,000,000			800,000,000
Common stock, par value | $ / shares	$ 0.0001		$ 0.0001			$ 0.0001
Common stock, shares issued			152,926,661		422,108	0
Common stock, shares outstanding			152,926,661			0
Common stock voting rights			Holders of such shares are entitled to one vote for each share of Class A common stock.
Number of votes for each share | Vote			1
Class A Common Stock | Other Nonoperating Income (Expense)
Class Of Stock [Line Items]
Recognition of distribution to non-redeeming shareholders | $			$ 3,888
Class X Common Stock
Class Of Stock [Line Items]
Common stock, terms of conversion			Each share of Class X common stock will:•Convert into one share of Class A common stock at the option of the holder. •Automatically convert into one share of Class A common stock upon a transfer of such share, other than to a Qualified Stockholder (as defined in the Amended and Restated Certificate of Incorporation of Starry Group, as filed as an exhibit to the Annual Report on March 31, 2022). •Automatically convert into one share of Class A common stock upon the earlier of (such date, the "Sunset Date"): (a) the date that is nine months following March 29, 2022 on which the holder (1) is no longer providing services as a member of the senior leadership team, officer or director and (2) has not provided any such services for the duration of such nine-month period; and (b) the first date after March 29, 2022 as of which the holder has transferred, in the aggregate, more than 75% of the shares of Class X common stock that were held by the holder immediately following the consummation of the Business Combination. Following such conversion, the reissuance of shares of Class X common stock will be prohibited. Non-redemption agreementsPursuant to the non-redemption agreements entered into with certain accredited investors (the "Non-Redeeming Shareholders") dated March 9, 2022, the Non-Redeeming Shareholders agreed to not redeem a certain number of shares of FirstMark Class A common stock. In connection with these agreements, the Company issued 422,108 shares of additional Class A common stock to the Non-Redeeming Shareholders subsequent to the close of the Business Combination (the "Non-Redemption Shares"). The Company evaluated the Non-Redeeming Shareholders' right to receive the additional shares of Class A common stock and concluded that the Non-Redemption Shares represented a non-pro rata distribution to the Non-Redeeming Shareholders. As a result, the Company recorded $3,888 in other income (expense), net on the condensed consolidated statement of operations and APIC on the condensed consolidated statement of stockholders' equity (deficit).
Common stock, shares authorized			50,000,000			50,000,000
Common stock, par value | $ / shares	$ 0.0001		$ 0.0001			$ 0.0001
Common stock, shares issued			9,268,335			0
Common stock, shares outstanding	9,268,335		9,268,335			0
Common stock voting rights			The holder of such shares is entitled to twenty votes for each share of Class X common stock, until the Sunset Date (defined below), and one vote for each share of Class X common stock from and after the Sunset Date.
Number of votes for each share | Vote			20
Prior to the Acquisition Merger | Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized				97,176,852		505,746,770
Preferred stock, shares issued				95,762,330
Preferred stock, shares outstanding				95,762,330
Prior to the Acquisition Merger | Series Seed Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized				9,761,747		53,030,270
Preferred stock, shares issued				9,761,745
Preferred stock, par value | $ / shares				$ 0.001
Preferred stock, shares outstanding				9,761,745
Prior to the Acquisition Merger | Series A Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized				16,852,283		91,549,300
Preferred stock, shares issued				16,852,283
Preferred stock, par value | $ / shares				$ 0.001
Preferred stock, shares outstanding				16,852,283
Prior to the Acquisition Merger | Series B Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized				10,207,696		55,452,865
Preferred stock, shares issued				10,207,696
Preferred stock, par value | $ / shares				$ 0.001
Preferred stock, shares outstanding				10,207,696
Prior to the Acquisition Merger | Series C Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized				19,965,160		108,459,871
Preferred stock, shares issued				19,965,160
Preferred stock, par value | $ / shares				$ 0.001
Preferred stock, shares outstanding				19,965,160
Prior to the Acquisition Merger | Series D Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized				16,090,802		87,412,587
Preferred stock, shares issued				16,090,802
Preferred stock, par value | $ / shares				$ 0.001
Preferred stock, shares outstanding				16,090,802
Prior to the Acquisition Merger | Series E Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized				19,299,164		104,841,877
Preferred stock, shares issued				18,751,311
Preferred stock, par value | $ / shares				$ 0.001
Preferred stock, shares outstanding				18,751,311
Prior to the Acquisition Merger | Series Z Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares authorized				5,000,000		5,000,000
Preferred stock, shares issued				4,133,333
Preferred stock, par value | $ / shares				$ 0.001
Preferred stock, shares outstanding				4,133,333