Loans Held for Investment and the Allowance for Credit Losses - Additional Information (Details)		3 Months Ended				9 Months Ended	12 Months Ended
		Dec. 31, 2020 USD ($) a Rating Loan LoanModification	Sep. 30, 2020 USD ($) Loan	Jun. 30, 2020 Loan	Mar. 31, 2020 USD ($) Loan	Sep. 30, 2020 USD ($) Loan	Dec. 31, 2020 USD ($) a Rating Loan LoanModification	Dec. 31, 2019 USD ($) Rating Loan	Dec. 31, 2018 USD ($)	Jan. 01, 2020 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Loans Held for Investment, Net (includes $2,259,467 and $2,585,030, respectively, pledged as collateral under secured credit facilities)		$ 4,456,460,000					$ 4,456,460,000	$ 4,980,389,000
Total loan commitment amount		4,943,511,000					4,943,511,000	5,628,765,000
Unfunded loan commitments		423,487,000					423,487,000	630,589,000
Unamortized loan discount and premium		$ 0					0	0
Cash consideration							131,902,000	59,759,000	$ 2,174,000
Gain (loss) on sale of investments								200,000
Loans and leases receivable loans sold							85,500,000
Extinguishment of unpaid principal balance							$ 112,000,000
Undeveloped commercially-zoned land | a		27					27
Loans Held for Investment	[1]	$ 4,516,400,000					$ 4,516,400,000	4,980,389,000
Net of an asset-specific credit loss reserve	[1]	59,940,000					59,940,000
Unamortized loan fees and discounts included in Loans Held for Investment		$ 8,300,000					$ 8,300,000	$ 17,800,000
Weighted Average Risk Rating | Rating		3.1					3.1	2.9
Description of loans reclassified into risk category							Company reclassified nine of its 10 hotel loans to risk category “4” due to anticipated operating challenges related to COVID-19.
Number of total hotel loans | Loan					10
Allowance for credit loss increase (decrease)							$ 43,200,000
Allowance for credit losses including realized loss							12,800,000
Allowance for credit losses on sale of loan							13,800,000
Allowance for credit loss reserve		$ 62,828,000					62,828,000
Loans Held for Investment		$ 4,516,400,000					$ 4,516,400,000	$ 4,980,389,000
Number of loan modification | LoanModification		3					17
Number of loan modification expiration | LoanModification		1					11
Number of loan modification renewed on tailored terms | LoanModification		1
Aggregate unpaid principal balance of loan repaid		$ 1,000,000,000.0					$ 1,000,000,000.0
Aggregate unpaid principal balance of loan outstanding		548,400,000					548,400,000
PIK interest		800,000					4,700,000
Real Estate
Accounts Notes And Loans Receivable [Line Items]
Allowance for credit loss reserve		$ 10,000,000.0					$ 10,000,000.0
Number of loans on non-accrual status | Loan		1					1	0
Amortized cost of loan		$ 31,100,000					$ 31,100,000	$ 30,600,000
Fair market value, discount rate		12.50%					12.50%
Fair market value, terminal capitalization rate		7.50%					7.50%
ASU 2016-13
Accounts Notes And Loans Receivable [Line Items]
Loans Held for Investment, Net (includes $2,259,467 and $2,585,030, respectively, pledged as collateral under secured credit facilities)										$ 4,962,606,000
Allowance for credit loss increase (decrease)					$ 19,600,000
Loans Held for Investment										$ 4,980,389,000
COVID-19
Accounts Notes And Loans Receivable [Line Items]
Total loan commitment amount		$ 212,500,000					$ 212,500,000
Weighted Average Risk Rating | Rating		3.1					3.1	2.9
Number of loans downgraded | Loan		2	1	1	9
Loans Held for Investment		$ 206,400,000					$ 206,400,000
Moved from Category 4 Risk Rating to Category 5 Risk Rating
Accounts Notes And Loans Receivable [Line Items]
Number of loans selected for risk rate changes | Loan						1	1
Moved from Category 2 Risk Rating to Category 3 Risk Rating
Accounts Notes And Loans Receivable [Line Items]
Number of loans selected for risk rate changes | Loan							1
Moved from Category 3 Risk Rating to Category 2 Risk Rating
Accounts Notes And Loans Receivable [Line Items]
Number of loans selected for risk rate changes | Loan						1
Moved from Category 4 Risk Rating to Category 3 Risk Rating
Accounts Notes And Loans Receivable [Line Items]
Loans and leases receivable unpaid principal balance		1,000,000.0	$ 3,000,000.0			$ 3,000,000.0	$ 1,000,000.0
Number of loans selected for risk rate changes | Loan			1
Rating 4
Accounts Notes And Loans Receivable [Line Items]
Loans Held for Investment		806,893,000					806,893,000	$ 208,300,000
Rating 4 | COVID-19
Accounts Notes And Loans Receivable [Line Items]
Number of hotel loans reclassified in to risk rate | Loan					9
Foreclosure Date
Accounts Notes And Loans Receivable [Line Items]
Principal balance sales, realized loss							12,800,000
Loans Held for Investment		99,200,000					99,200,000
Net of an asset-specific credit loss reserve		12,800,000					12,800,000
Floating Rate Performing Mortgage Loan
Accounts Notes And Loans Receivable [Line Items]
Total loan commitment amount								64,900,000
Loans and leases receivable unpaid principal balance								59,600,000
Cash consideration								$ 59,800,000
Loans and leases receivable loans sold							$ 85,500,000
Six Loan
Accounts Notes And Loans Receivable [Line Items]
Number of mortgage loans originated or acquired | Loan							6
Total loan commitment amount		526,300,000					$ 526,300,000
Loans and leases receivable unpaid principal balance		431,900,000					431,900,000
Unfunded loan commitments		94,400,000					$ 94,400,000
One Loan
Accounts Notes And Loans Receivable [Line Items]
Number of mortgage loans originated or acquired | Loan							1
Loans and leases receivable unpaid principal balance		78,400,000					$ 78,400,000
Loans and leases receivable expected initial unpaid principal balance		99,300,000					99,300,000
Principal balance sales, realized loss							13,800,000
One Loan | Floating Rate Performing Mortgage Loan
Accounts Notes And Loans Receivable [Line Items]
Loans and leases receivable expected initial unpaid principal balance		99,300,000					99,300,000
Originated or Acquired 32 Mortgage Loans
Accounts Notes And Loans Receivable [Line Items]
Number of mortgage loans originated or acquired | Loan								32
Total loan commitment amount								$ 2,900,000,000
Loans and leases receivable unpaid principal balance								2,400,000,000
Unfunded loan commitments								439,500,000
Subordinated and Mezzanine Loans
Accounts Notes And Loans Receivable [Line Items]
Total loan commitment amount		50,000,000.0					50,000,000.0
Loans and leases receivable loans sold							46,400,000
First Mortgage
Accounts Notes And Loans Receivable [Line Items]
Total loan commitment amount		300,800,000					300,800,000
Loans and leases receivable unpaid principal balance		279,200,000					279,200,000
Principal balance sales, realized loss							12,800,000
Extinguishment of unpaid principal balance							$ 112,000,000.0
Loans and leases receivable, maturity date							Oct. 09, 2020
Accrued Interest and Fees Receivable
Accounts Notes And Loans Receivable [Line Items]
Loans Held for Investment, Net (includes $2,259,467 and $2,585,030, respectively, pledged as collateral under secured credit facilities)		$ 14,000,000.0					$ 14,000,000.0	$ 19,500,000

[1] The Company’s consolidated Total Assets and Total Liabilities at December 31, 2020 include the assets and liabilities of variable interest entities (“VIEs”) of $2.3 billion and $1.8 billion , respectively. The Company’s Total Assets and Total Liabilities at December 31, 2019 include assets and liabilities of VIEs of $2.2 billion and $1.8 billion, respectively. These assets can be used only to satisfy obligations of the VIEs, and creditors of the VIEs have recourse only to those assets, and not to TPG RE Finance Trust, Inc. See Note 6 to the Consolidated Financial Statements for details