Mortgage Notes Receivable - Information pertaining to mortgage notes receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Loans and Leases Receivable Disclosure [Line Items]
Total principal outstanding for our mortgage notes receivable	$ 825,397		$ 809,076
Allowance for loan losses	10,943	$ 10,663	10,590	$ 13,494	$ 9,966	$ 4,096
Mortgage notes receivable, net	814,454		798,486
Mortgage notes receivables
Loans and Leases Receivable Disclosure [Line Items]
Total loan commitments	1,328,556		1,245,963
Construction holdbacks	412,751		356,026
Interest reserves	35,600		29,817
Private REIT participation	41,427		37,729
Total principal outstanding for our mortgage notes receivable	838,778		822,391
Allowance for loan losses	10,943		10,590
Deferred origination and amendment fees	13,381		13,315
Mortgage notes receivable, net	814,454		798,486
Broadmark Private REIT, LLC
Loans and Leases Receivable Disclosure [Line Items]
Construction holdbacks	34,700		40,400
Interest reserves	2,600		4,300
Unfunded Loan Commitment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for loan losses	725	947
Unfunded Loan Commitment [Member] | Accounts payable and accrued liabilities
Loans and Leases Receivable Disclosure [Line Items]
Allowance for loan losses	700
Funded And Unfunded Loan Commitment [Member]
Loans and Leases Receivable Disclosure [Line Items]
Allowance for loan losses	$ 11,668	$ 11,610	$ 10,590