Borrowings - Debt Securitizations (Details) - USD ($)		9 Months Ended
	Jun. 29, 2021	Sep. 30, 2022	Sep. 30, 2021	Jun. 09, 2022	Mar. 15, 2022	Dec. 31, 2021	Dec. 15, 2021	Nov. 01, 2021
Debt Instrument [Line Items]
Aggregate Principal Committed		$ 35,414,783,000				$ 23,121,914,000
Borrowings on debt		17,575,191,000	$ 14,514,975,000
2021-1 BSL Debt
Debt Instrument [Line Items]
Outstanding Principal		819,500,000
2021-1 BSL Debt | Secured debt
Debt Instrument [Line Items]
Aggregate Principal Committed	$ 876,600,000	663,000,000				663,000,000
Borrowings on debt	819,500,000
Outstanding Principal		663,000,000				663,000,000
2021-1 BSL Debt | Subordinated Debt
Debt Instrument [Line Items]
Outstanding Principal		156,500,000
2021-1 BSL, Senior Secured Floating Rate, Class A Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 499,800,000
2021-1 BSL, Senior Secured Floating Rate, Class A Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		1.25%
2021-1 BSL, Senior Secured Floating Rate, Class B Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 38,760,000
2021-1 BSL, Senior Secured Floating Rate, Class B Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		1.80%
2021-1 BSL, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 59,160,000
2021-1 BSL, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		2.15%
2021-1 BSL, Mezzanine Secured Deferrable Floating Rate, Class D Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 65,280,000
2021-1 BSL, Mezzanine Secured Deferrable Floating Rate, Class D Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		3.35%
2021-1 BSL, Junior Secured Deferrable Floating Rate | Secured debt
Debt Instrument [Line Items]
Aggregate Principal Committed	$ 57,100,000
Outstanding Principal		$ 0
2021-1 BSL, Junior Secured Deferrable Floating Rate | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		7.00%
2021-2 Debt
Debt Instrument [Line Items]
Outstanding Principal		$ 603,650,000
2021-2 Debt | Secured debt
Debt Instrument [Line Items]
Aggregate Principal Committed		505,800,000				505,800,000		$ 603,700,000
Outstanding Principal		505,800,000				$ 505,800,000
2021-2 Debt | Subordinated Debt
Debt Instrument [Line Items]
Outstanding Principal		97,850,000
2021-2 Debt, Senior Secured Floating Rate, Class A-L Loans | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 218,000,000
2021-2 Debt, Senior Secured Floating Rate, Class A-L Loans | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		1.22%
2021-2 Debt, Senior Secured Floating Rate, Class A Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 149,500,000
2021-2 Debt, Senior Secured Floating Rate, Class A Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		1.22%
2021-2 Notes, Senior Secured Floating Rate, Class B Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 38,100,000
2021-2 Notes, Senior Secured Floating Rate, Class B Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		1.75%
2021-2 Notes, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 48,000,000
2021-2 Notes, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		2.05%
2021-2 Notes, Mezzanine Secured Deferrable Floating Rate, Class D Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 52,200,000
2021-2 Notes, Mezzanine Secured Deferrable Floating Rate, Class D Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		3.15%
2021-1 MML Debt
Debt Instrument [Line Items]
Outstanding Principal		$ 1,001,000,000
2021-1 MML Debt | Secured debt
Debt Instrument [Line Items]
Aggregate Principal Committed							$ 1,001,000,000
Outstanding Principal		690,000,000
2021-1 MML Debt | Subordinated Debt
Debt Instrument [Line Items]
Outstanding Principal		311,000,000
2021-1 MML Debt, Senior Secured Floating Rate, Class A Loans | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 50,000,000
2021-1 MML Debt, Senior Secured Floating Rate, Class A Loans | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		1.48%
2021-1 MML Debt, Senior Secured Floating Rate, Class A Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 480,000,000
2021-1 MML Debt, Senior Secured Floating Rate, Class A Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		1.48%
2021-1 MML Debt, Senior Secured Floating Rate, Class B Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 80,000,000
2021-1 MML Debt, Senior Secured Floating Rate, Class B Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		1.90%
2021-1 MML Debt, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 80,000,000
2021-1 MML Debt, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt | LIBOR
Debt Instrument [Line Items]
Applicable margin rate		2.60%
2022-1 MML Debt
Debt Instrument [Line Items]
Outstanding Principal		$ 1,090,360,000
2022-1 MML Debt | Secured debt
Debt Instrument [Line Items]
Aggregate Principal Committed					$ 1,090,000,000.00
Outstanding Principal		759,000,000
2022-1 MML Debt | Subordinated Debt
Debt Instrument [Line Items]
Outstanding Principal		331,360,000
2022-1 MML Debt, Senior Secured Floating Rate, Class A-1 Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 525,000,000
2022-1 MML Debt, Senior Secured Floating Rate, Class A-1 Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		1.65%
2022-1 MML Debt, Senior Secured Fixed, Class A-2 Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 80,000,000
Interest rate		3.41%
2022-1 MML Debt, Senior Secured Floating Rate, Class B Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 66,000,000
2022-1 MML Debt, Senior Secured Floating Rate, Class B Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		2.00%
2022-1 MML Debt, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 88,000,000
2022-1 MML Debt, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		2.75%
2022-1 BSL Debt
Debt Instrument [Line Items]
Outstanding Principal		$ 589,750,000
2022-1 BSL Debt | Secured debt
Debt Instrument [Line Items]
Aggregate Principal Committed		420,000,000		$ 589,750,000
Outstanding Principal		531,000,000
2022-1 BSL Debt | Subordinated Debt
Debt Instrument [Line Items]
Outstanding Principal		58,750,000
2022-1 BSL Debt, Senior Secured Floating Rate, Class A-1A Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 292,000,000
2022-1 BSL Debt, Senior Secured Floating Rate, Class A-1A Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		1.58%
2022-1 BSL Debt, Senior Secured Fixed Rate, Class A-1B Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 50,000,000
Interest rate		4.34%
2022-1 BSL Debt, Senior Secured Floating Rate, Class A-2 Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 12,000,000
2022-1 BSL Debt, Senior Secured Floating Rate, Class A-2 Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		2.00%
2022-1 BSL Debt, Senior Secured Floating Rate, Class B-1 Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 40,000,000
2022-1 BSL Debt, Senior Secured Floating Rate, Class B-1 Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		2.35%
2022-1 BSL Debt, Senior Secured Fixed Rate, Class B-2 Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 26,000,000
Interest rate		4.98%
2022-1 BSL Debt, Secured Deferrable Floating Rate, Class C Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 51,000,000
2022-1 BSL Debt, Secured Deferrable Floating Rate, Class C Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		2.60%
2022-1 BSL Debt, Mezzanine Secured Deferrable Floating Rate, Class D Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 39,000,000
2022-1 BSL Debt, Mezzanine Secured Deferrable Floating Rate, Class D Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		3.69%
2022-1 BSL Debt, Mezzanine Secured Deferrable Floating Rate, Class E Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 21,000,000
2022-1 BSL Debt, Mezzanine Secured Deferrable Floating Rate, Class E Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		7.33%
MML 2022-2 Debt
Debt Instrument [Line Items]
Outstanding Principal		$ 498,105,000
MML 2022-2 Debt | Secured debt
Debt Instrument [Line Items]
Aggregate Principal Committed		300,500,000		$ 498,105,000
Outstanding Principal		341,000,000
MML 2022-2 Debt | Subordinated Debt
Debt Instrument [Line Items]
Outstanding Principal		157,105,000
MML 2022-2 Debt, Senior Secured Floating Rate, Class A-L Loans | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 275,000,000
MML 2022-2 Debt, Senior Secured Floating Rate, Class A-L Loans | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		2.10%
MML 2022-2 Debt, Senior Secured Floating Rate, Class B-1 Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 14,000,000
MML 2022-2 Debt, Senior Secured Floating Rate, Class B-1 Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		3.35%
MML 2022-2 Debt, Senior Secured Fixed Rate, Class B-2 Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 11,500,000
Interest rate		5.88%
MML 2022-2 Debt, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt
Debt Instrument [Line Items]
Outstanding Principal		$ 40,500,000
MML 2022-2 Debt, Mezzanine Secured Deferrable Floating Rate, Class C Notes | Secured debt | SOFR
Debt Instrument [Line Items]
Applicable margin rate		2.50%