CONVERTIBLE PREFERRED STOCK AND EQUITY - Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 30, 2021		Mar. 31, 2021	Dec. 31, 2020		Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				63,877,518
Redeemable convertible preferred stock, outstanding (in shares)	0		63,756,000	63,756,438		63,756,000	63,756,000	61,288,000
Redeemable convertible preferred stock, issued (in shares)				63,756,438
Redeemable convertible preferred stock	$ 0	[1]	$ 160,605	$ 160,605	[1]	$ 160,605	$ 160,605	$ 150,305
Redeemable convertible preferred stock, liquidation preference				$ 165,562
Legacy Latch
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				71,204,000
Redeemable convertible preferred stock, outstanding (in shares)				71,069,000
Redeemable convertible preferred stock, issued (in shares)				71,069,000
Redeemable convertible preferred stock				$ 160,605
Redeemable convertible preferred stock, liquidation preference				$ 165,562
Series Seed | Legacy Latch
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				3,971,000
Redeemable convertible preferred stock, outstanding (in shares)				3,971,000
Redeemable convertible preferred stock, issued (in shares)				3,971,000
Issuance price per share (in dollars per share)				$ 0.60
Redeemable convertible preferred stock				$ 1,768
Redeemable convertible preferred stock, liquidation preference				$ 4,978
Series Seed | Legacy Latch
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				4,000,000
Redeemable convertible preferred stock, outstanding (in shares)				4,000,000
Redeemable convertible preferred stock, issued (in shares)				4,000,000
Issuance price per share (in dollars per share)				$ 0.63
Redeemable convertible preferred stock				$ 2,479
Redeemable convertible preferred stock, liquidation preference				$ 5,101
Series A | Legacy Latch
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				15,231,000
Redeemable convertible preferred stock, outstanding (in shares)				15,231,000
Redeemable convertible preferred stock, issued (in shares)				15,231,000
Issuance price per share (in dollars per share)				$ 0.75
Redeemable convertible preferred stock				$ 11,110
Redeemable convertible preferred stock, liquidation preference				$ 11,367
Series A-1 | Legacy Latch
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				8,464,000
Redeemable convertible preferred stock, outstanding (in shares)				8,464,000
Redeemable convertible preferred stock, issued (in shares)				8,464,000
Issuance price per share (in dollars per share)				$ 1.18
Redeemable convertible preferred stock				$ 9,737
Redeemable convertible preferred stock, liquidation preference				$ 10,000
Series B | Legacy Latch
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				15,983,000
Redeemable convertible preferred stock, outstanding (in shares)				15,983,000
Redeemable convertible preferred stock, issued (in shares)				15,983,000
Issuance price per share (in dollars per share)				$ 3.13
Redeemable convertible preferred stock				$ 50,000
Redeemable convertible preferred stock, liquidation preference				$ 50,000
Series B - 2019 Convertible Notes conversion at 10% discount | Legacy Latch
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				2,753,000
Redeemable convertible preferred stock, outstanding (in shares)				2,753,000
Redeemable convertible preferred stock, issued (in shares)				2,753,000
Issuance price per share (in dollars per share)				$ 2.82
Redeemable convertible preferred stock				$ 8,601
Redeemable convertible preferred stock, liquidation preference				$ 7,752
Series B-1 | Legacy Latch
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				18,112,000
Redeemable convertible preferred stock, outstanding (in shares)				17,977,000
Redeemable convertible preferred stock, issued (in shares)				17,977,000
Issuance price per share (in dollars per share)				$ 3.74
Redeemable convertible preferred stock				$ 66,842
Redeemable convertible preferred stock, liquidation preference				$ 67,300
Series B-2 | Legacy Latch
Class of Stock [Line Items]
Redeemable convertible preferred stock, authorized (in shares)				2,690,000
Redeemable convertible preferred stock, outstanding (in shares)				2,690,000
Redeemable convertible preferred stock, issued (in shares)				2,690,000
Issuance price per share (in dollars per share)				$ 3.37
Redeemable convertible preferred stock				$ 10,068
Redeemable convertible preferred stock, liquidation preference				$ 9,064

[1] Shares outstanding for all periods reflect the adjustment for the Exchange Ratio as a result of the Business Combination. Shares issued and outstanding as of June 30, 2021 excludes 738,000 shares subject to vesting requirements. See Note 1, Description of Business.