Fair Value Measurements - Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Short-Term Borrowings	$ 420,829	$ 28,546
Total	30,552,444	23,061,312
Bard Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	1,000,298	242,243
Castle Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	1,194,401	1,121,681
Summit Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	952,105	286,046
Denali Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	562,800	562,800
Bushnell Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	480,300	465,300
Granite Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	493,554	563,600
Middle Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	750,000	600,950
Bison Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	1,203,200	703,200
Blanca Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	1,375,090	1,375,090
Windom Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	1,029,841	967,477
Monarch Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	750,000	1,400,400
Borah Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	0	130,000
Naomi Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	0	385,000
Meridian Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	246,000	246,000
Haydon Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	250,000	49,000
Bear Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	164,816	360,531
Phoenix Peak Funding Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	197,736	0
Revolving Credit Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	4,639,587	1,131,025
June 2024 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	0	427,693
June 2026 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	384,560	379,251
May 2027 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	624,500	618,319
October 2027 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	357,070	368,331
September 2024 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	0	354,580
December 2026 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	1,191,500	1,137,187
November 2026 Eurobonds \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	499,280	501,901
November 2024 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	0	485,177
March 2027 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	957,000	921,525
January 2025 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	499,490	483,120
January 2029 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	614,770	597,773
March 2025 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	898,740	885,149
April 2026 UK Bonds \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	308,406	306,018
September 2025 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	811,920	814,554
November 2028 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	526,100	520,940
January 2031 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	508,650	0
July 2029 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	503,550	0
September 2027 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	395,320	0
April 2030 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	389,240	0
November 2029 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	395,160	0
November 2034 Notes \| Unsecured debt
Debt Instrument [Line Items]
Fair Value	781,120	0
2021-1 BSL Notes \| Secured debt
Debt Instrument [Line Items]
Fair Value	663,000	663,000
MML 2021-1 Debt \| Secured debt
Debt Instrument [Line Items]
Fair Value	690,000	690,000
MML 2022-1 Debt \| Secured debt
Debt Instrument [Line Items]
Fair Value	759,000	756,862
2022-1 BSL Debt \| Secured debt
Debt Instrument [Line Items]
Fair Value	420,000	420,000
2021-2 Notes \| Secured debt
Debt Instrument [Line Items]
Fair Value	505,800	505,800
MML 2022-2 Debt \| Secured debt
Debt Instrument [Line Items]
Fair Value	300,373	300,273
2023-1 Notes \| Secured debt
Debt Instrument [Line Items]
Fair Value	308,039	304,970
2024-1 Notes \| Secured debt
Debt Instrument [Line Items]
Fair Value	244,264	0
2024-2 Notes \| Secured debt
Debt Instrument [Line Items]
Fair Value	$ 305,035	$ 0

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

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