Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value by Hierarchy Level (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	$ 149,541	$ 112,139
Other invested assets—at fair value	8,492	5,511
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	5,884,176	5,692,276
Derivative assets	2,563	11
Total assets at fair value	6,036,280	5,804,426
Derivative liabilities	577	4,900
Total liabilities at fair value	577	4,900
Level I | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	495,480	520,167
Derivative assets	0	0
Total assets at fair value	566,005	584,721
Derivative liabilities	0	0
Total liabilities at fair value	0	0
Level II | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	5,379,180	5,165,313
Derivative assets	2,426	11
Total assets at fair value	5,460,622	5,212,909
Derivative liabilities	15	42
Total liabilities at fair value	15	42
Level III | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	9,516	6,796
Derivative assets	137	0
Total assets at fair value	9,653	6,796
Derivative liabilities	562	4,858
Total liabilities at fair value	562	4,858
Loaned securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	78,762
Loaned securities | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	79,016	47,585
Loaned securities | Fair Value, Measurements, Recurring | Mortgage insurance-linked notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	0
Loaned securities | Fair Value, Measurements, Recurring | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	70,525	64,554
Loaned securities | Level I | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	0	0
Loaned securities | Level I | Fair Value, Measurements, Recurring | Mortgage insurance-linked notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	0
Loaned securities | Level I | Fair Value, Measurements, Recurring | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	70,525	64,554
Loaned securities | Level II | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	79,016	47,585
Loaned securities | Level II | Fair Value, Measurements, Recurring | Mortgage insurance-linked notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	0
Loaned securities | Level II | Fair Value, Measurements, Recurring | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	0	0
Loaned securities | Level III | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	0	0
Loaned securities | Level III | Fair Value, Measurements, Recurring | Mortgage insurance-linked notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	0
Loaned securities | Level III | Fair Value, Measurements, Recurring | Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loaned securities	0	0
Fixed-maturities available for sale | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	5,037,747	5,017,711
Fixed-maturities available for sale | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	135,178	145,442
Fixed-maturities available for sale | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	133,569	142,386
Fixed-maturities available for sale | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	2,379,958	2,490,582
Fixed-maturities available for sale | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	959,210	928,399
Fixed-maturities available for sale | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	560,352	593,357
Fixed-maturities available for sale | Fair Value, Measurements, Recurring | CLO
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	493,677	498,192
Fixed-maturities available for sale | Fair Value, Measurements, Recurring | Other ABS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	320,088	161,359
Fixed-maturities available for sale | Fair Value, Measurements, Recurring | Foreign government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	5,033	4,975
Fixed-maturities available for sale | Fair Value, Measurements, Recurring | Mortgage insurance-linked notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	50,682	53,019
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	125,053	140,011
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	125,053	140,011
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring | CLO
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring | Other ABS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring | Foreign government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level I | Fair Value, Measurements, Recurring | Mortgage insurance-linked notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	4,912,694	4,877,700
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	10,125	5,431
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	133,569	142,386
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	2,379,958	2,490,582
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	959,210	928,399
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	560,352	593,357
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring | CLO
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	493,677	498,192
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring | Other ABS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	320,088	161,359
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring | Foreign government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	5,033	4,975
Fixed-maturities available for sale | Level II | Fair Value, Measurements, Recurring | Mortgage insurance-linked notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	50,682	53,019
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring | CLO
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring | Other ABS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring | Foreign government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Fixed-maturities available for sale | Level III | Fair Value, Measurements, Recurring | Mortgage insurance-linked notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	99,769	115,665
Trading securities | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	66,554	70,511
Trading securities | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	22,798	32,827
Trading securities | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	5,883	6,847
Trading securities | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	4,534	5,480
Trading securities | Level I | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Level I | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Level I | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Level I | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Level I | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Level II | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	99,769	115,665
Trading securities | Level II | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	66,554	70,511
Trading securities | Level II | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	22,798	32,827
Trading securities | Level II | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	5,883	6,847
Trading securities | Level II | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	4,534	5,480
Trading securities | Level III | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Level III | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Level III | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Level III | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Trading securities | Level III | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Equity securities | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	108,911	148,965
Equity securities | Level I | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	100,194	138,716
Equity securities | Level II | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	6,217	7,749
Equity securities | Level III | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	2,500	2,500
Mortgage loans held for sale | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	138,289	3,549
Mortgage loans held for sale | Level I | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Mortgage loans held for sale | Level II | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	138,289	3,549
Mortgage loans held for sale | Level III | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Other investments | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	7,016	4,296
Other investments | Level I | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Other investments | Level II | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Other investments | Level III | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	7,016	4,296
Short-term investments | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	492,444	402,090
Short-term investments | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	7,727
Short-term investments | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	2,500	2,785
Short-term investments | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	104,899	42,385
Short-term investments | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	1,620
Short-term investments | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	1,336
Short-term investments | Fair Value, Measurements, Recurring | Other ABS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	7,069
Short-term investments | Fair Value, Measurements, Recurring | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	104,787	115,480
Short-term investments | Fair Value, Measurements, Recurring | Money market instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	262,506	241,440
Short-term investments | Level I | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	270,233	241,440
Short-term investments | Level I | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	7,727
Short-term investments | Level I | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Short-term investments | Level I | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Short-term investments | Level I | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0
Short-term investments | Level I | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0
Short-term investments | Level I | Fair Value, Measurements, Recurring | Other ABS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0
Short-term investments | Level I | Fair Value, Measurements, Recurring | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Short-term investments | Level I | Fair Value, Measurements, Recurring | Money market instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	262,506	241,440
Short-term investments | Level II | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	222,211	160,650
Short-term investments | Level II | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0
Short-term investments | Level II | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	2,500	2,785
Short-term investments | Level II | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	104,899	42,385
Short-term investments | Level II | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	1,620
Short-term investments | Level II | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	1,336
Short-term investments | Level II | Fair Value, Measurements, Recurring | Other ABS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	7,069
Short-term investments | Level II | Fair Value, Measurements, Recurring | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	104,787	115,480
Short-term investments | Level II | Fair Value, Measurements, Recurring | Money market instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Short-term investments | Level III | Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Short-term investments | Level III | Fair Value, Measurements, Recurring | U.S. government and agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0
Short-term investments | Level III | Fair Value, Measurements, Recurring | State and municipal obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Short-term investments | Level III | Fair Value, Measurements, Recurring | Corporate bonds and notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Short-term investments | Level III | Fair Value, Measurements, Recurring | RMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0
Short-term investments | Level III | Fair Value, Measurements, Recurring | CMBS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0
Short-term investments | Level III | Fair Value, Measurements, Recurring | Other ABS
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0
Short-term investments | Level III | Fair Value, Measurements, Recurring | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Short-term investments | Level III | Fair Value, Measurements, Recurring | Money market instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	0	0
Partnership investments | Investments measured at NAV
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other invested assets—at fair value	$ 1,500	$ 1,200