Mortgage Notes Receivable - Information pertaining to mortgage notes receivable (Details) - USD ($) $ in Thousands		Dec. 31, 2021		Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019	[1]	Nov. 14, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Total principal outstanding for our mortgage notes receivable		$ 911,744			$ 809,076
Adoption of ASU 2016-13		10,394			10,590	$ 4,096		$ 4,594	$ 1,704
Mortgage notes receivable, net		901,350			798,486
Mortgage notes receivables
Loans and Leases Receivable Disclosure [Line Items]
Total loan commitments		1,489,055			1,245,963
Construction holdbacks		524,462	[2]		356,026
Interest reserves		39,880	[2]		29,817
Private REIT participation			[3]		37,729
Total principal outstanding for our mortgage notes receivable		924,713			822,391
Adoption of ASU 2016-13		10,394	[4]		10,590
Deferred origination and amendment fees		12,969			13,315
Mortgage notes receivable, net		901,350			798,486
Broadmark Private REIT, LLC
Loans and Leases Receivable Disclosure [Line Items]
Construction holdbacks					40,400
Interest reserves					4,300
Unfunded Loan Commitment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Adoption of ASU 2016-13	[5]	904			0
Unfunded Loan Commitment [Member] | Accounts payable and accrued liabilities
Loans and Leases Receivable Disclosure [Line Items]
Adoption of ASU 2016-13		900		$ 900
Funded And Unfunded Loan Commitment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Adoption of ASU 2016-13		$ 11,298			$ 10,590

[1] The beginning balance on November 15, 2019 (Successor) represents the allowance of the acquirer, BRELF II

[2] Includes construction holdbacks of $40.4 million and interest reserves of $4.3 million on participating interests sold to the Private REIT as of December 31, 2020. As of December 31, 2021, there were no outstanding participations as a result of the liquidation of the Private REIT and purchase of all outstanding participations by the Company. Refer to Note 13 for details.

[3] The Private REIT’s participations in loans originated by us met the characteristics of participating interests and the criterion for sale accounting and therefore, were derecognized from our consolidated financial statements. As of December 31, 2021, there were no outstanding participations as a result of the liquidation of the Private REIT and purchase of all outstanding participations by the Company. Refer to Note 13 for details.

[4] As of December 31, 2021, $0.9 million of the CECL allowance is excluded from this table because it relates to unfunded commitments and has been recorded as a liability under accounts payable and accrued liabilities in our consolidated balance sheet.

[5] CECL allowance related to unfunded commitments is presented as a liability under accounts payable and accrued liabilities in our consolidated balance sheet.