DESCRIPTION OF BUSINESS AND ACCOUNTING POLICIES - Impact of the Correction on the Company's Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands		Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
WARRANT LIABILITIES		$ 0		$ 47,349
Total liabilities	[1]	6,605,754		622,924
Additional paid-in capital		3,877,418		2,596,012
Accumulated deficit		(1,514,509)		(1,043,449)
Total shareholders’ equity		$ 2,362,861	$ 2,417,921	1,552,658	$ (708,650)	$ (843,519)	$ (733,103)
Previously Stated
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
WARRANT LIABILITIES				0
Total liabilities				575,575
Additional paid-in capital				2,677,155
Accumulated deficit				(1,077,243)
Total shareholders’ equity				1,600,007
Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
WARRANT LIABILITIES				47,349
Total liabilities				47,349
Additional paid-in capital				(81,143)
Accumulated deficit				33,794
Total shareholders’ equity				$ (47,349)

[1] The Company’s consolidated liabilities at September 30, 2021 and December 31, 2020 include the following liabilities for which the VIE creditors do not have recourse to Opendoor: Accounts payable and other accrued liabilities, $66,134 and $2,335; Interest payable, $9,413 and $1,059; Current portion of non-recourse asset-backed debt, $4,049,812 and $339,173; Non-recourse asset-backed debt, net of current portion, $1,367,989 and $135,467; and Total liabilities, $5,493,348 and $478,034, respectively.