Fair Value Measurements - Categorized Investments and Assets Carried at Cost or Amortized Cost and Fair Value Among Levels (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	$ 729,721	$ 367,125
Total investments	9,612,888	8,697,892
Reinsurance balances recoverable on paid and unpaid losses	(88,086)	(130,739)
Other Assets:
Losses and LAE	2,621,122	2,874,055
U.S. government and agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	736,043	510,245
U.K. government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	161,772	300,631
Corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	5,697,067	4,839,840
Municipal
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	167,882	130,265
Residential mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	471,836	773,557
Commercial mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	900,029	713,063
Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	775,402	636,481
Private equity funds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	268,800
CLO equities | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	87,600
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	729,721	367,125
Total investments	12,881,236	11,037,554
Cash and cash equivalents	396,083	264,985
Other Assets:
Losses and LAE	2,621,122	2,874,055
Recurring | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	9,612,888	8,697,892
Recurring | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	2,524,420	1,957,757
Recurring | Reinsurance balances recoverable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Reinsurance balances recoverable on paid and unpaid losses	695,518	739,591
Recurring | Other Assets
Other Assets:
Derivative instruments	2,011	6,701
Recurring | Other Liabilities
Other Liabilities:
Derivative instruments	15,558	983
Recurring | Designated as Hedging Instrument | Other Assets
Other Assets:
Derivative instruments	642	1,615
Recurring | Designated as Hedging Instrument | Other Liabilities
Other Liabilities:
Derivative instruments	11,452	300
Recurring | Not Designated as Hedging Instrument | Other Assets
Other Assets:
Derivative instruments	1,369	5,086
Recurring | Not Designated as Hedging Instrument | Other Liabilities
Other Liabilities:
Derivative instruments	4,106	683
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	430,357	102,102
Total investments	430,357	102,102
Cash and cash equivalents	173,892	243,839
Other Assets:
Losses and LAE	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Reinsurance balances recoverable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Reinsurance balances recoverable on paid and unpaid losses	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Assets
Other Assets:
Derivative instruments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Liabilities
Other Liabilities:
Derivative instruments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Designated as Hedging Instrument | Other Assets
Other Assets:
Derivative instruments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Designated as Hedging Instrument | Other Liabilities
Other Liabilities:
Derivative instruments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Not Designated as Hedging Instrument | Other Assets
Other Assets:
Derivative instruments	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Not Designated as Hedging Instrument | Other Liabilities
Other Liabilities:
Derivative instruments	0	0
Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	30,565	36,313
Total investments	10,166,877	9,086,971
Cash and cash equivalents	222,191	21,146
Other Assets:
Losses and LAE	0	0
Recurring | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	9,612,888	8,643,996
Recurring | Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	509,217	391,882
Recurring | Significant Other Observable Inputs (Level 2) | Reinsurance balances recoverable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Reinsurance balances recoverable on paid and unpaid losses	0	0
Recurring | Significant Other Observable Inputs (Level 2) | Other Assets
Other Assets:
Derivative instruments	2,011	6,701
Recurring | Significant Other Observable Inputs (Level 2) | Other Liabilities
Other Liabilities:
Derivative instruments	15,558	983
Recurring | Significant Other Observable Inputs (Level 2) | Designated as Hedging Instrument | Other Assets
Other Assets:
Derivative instruments	642	1,615
Recurring | Significant Other Observable Inputs (Level 2) | Designated as Hedging Instrument | Other Liabilities
Other Liabilities:
Derivative instruments	11,452	300
Recurring | Significant Other Observable Inputs (Level 2) | Not Designated as Hedging Instrument | Other Assets
Other Assets:
Derivative instruments	1,369	5,086
Recurring | Significant Other Observable Inputs (Level 2) | Not Designated as Hedging Instrument | Other Liabilities
Other Liabilities:
Derivative instruments	4,106	683
Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	268,799	228,710
Total investments	356,668	321,973
Cash and cash equivalents	0	0
Other Assets:
Losses and LAE	2,621,122	2,874,055
Recurring | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	53,896
Recurring | Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	87,869	39,367
Recurring | Significant Unobservable Inputs (Level 3) | Reinsurance balances recoverable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Reinsurance balances recoverable on paid and unpaid losses	695,518	739,591
Recurring | Significant Unobservable Inputs (Level 3) | Other Assets
Other Assets:
Derivative instruments	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Other Liabilities
Other Liabilities:
Derivative instruments	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Designated as Hedging Instrument | Other Assets
Other Assets:
Derivative instruments	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Designated as Hedging Instrument | Other Liabilities
Other Liabilities:
Derivative instruments	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Not Designated as Hedging Instrument | Other Assets
Other Assets:
Derivative instruments	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Not Designated as Hedging Instrument | Other Liabilities
Other Liabilities:
Derivative instruments	0	0
Recurring | Fair Value Based on NAV as Practical Expedient
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	1,927,334	1,526,508
Recurring | Fair Value Based on NAV as Practical Expedient | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	1,927,334	1,526,508
Recurring | U.S. government and agency | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	736,043	510,245
Recurring | U.S. government and agency | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | U.S. government and agency | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	736,043	510,245
Recurring | U.S. government and agency | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | U.K. government | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	161,772	300,631
Recurring | U.K. government | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | U.K. government | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	161,772	300,631
Recurring | U.K. government | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Other government | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	702,857	793,810
Recurring | Other government | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Other government | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	702,857	793,810
Recurring | Other government | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Corporate | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	5,697,067	4,839,840
Recurring | Corporate | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Corporate | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	5,697,067	4,802,454
Recurring | Corporate | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	37,386
Recurring | Municipal | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	167,882	130,265
Recurring | Municipal | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Municipal | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	167,882	130,265
Recurring | Municipal | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Residential mortgage-backed | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	471,836	773,557
Recurring | Residential mortgage-backed | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Residential mortgage-backed | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	471,836	773,557
Recurring | Residential mortgage-backed | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Commercial mortgage-backed | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	900,029	713,063
Recurring | Commercial mortgage-backed | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Commercial mortgage-backed | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	900,029	705,674
Recurring | Commercial mortgage-backed | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	7,389
Recurring | Asset-backed | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	775,402	636,481
Recurring | Asset-backed | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Asset-backed | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	775,402	627,360
Recurring | Asset-backed | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	9,121
Recurring | Funds Held - Directly Managed | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	14,207	14,780
Recurring | Funds Held - Directly Managed | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Funds Held - Directly Managed | Significant Other Observable Inputs (Level 2) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	14,207	14,780
Recurring | Funds Held - Directly Managed | Significant Unobservable Inputs (Level 3) | Fixed maturity investments, trading
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturity investments	0	0
Recurring | Publicly traded equity investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	327,875	138,415
Recurring | Publicly traded equity investments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	297,310	102,102
Recurring | Publicly traded equity investments | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	30,565	36,313
Recurring | Publicly traded equity investments | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	0	0
Recurring | Exchange-traded funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	133,047
Recurring | Exchange-traded funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	133,047
Recurring | Exchange-traded funds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	0
Recurring | Exchange-traded funds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	0
Recurring | Private equity funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	268,799	228,710
Recurring | Private equity funds | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	329,885	248,628
Recurring | Private equity funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	0	0
Recurring | Private equity funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Private equity funds | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	0	0
Recurring | Private equity funds | Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Private equity funds | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments	268,799	228,710
Recurring | Private equity funds | Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Private equity funds | Fair Value Based on NAV as Practical Expedient | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	329,885	248,628
Recurring | Hedge funds | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	1,121,904	852,584
Recurring | Hedge funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Hedge funds | Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Hedge funds | Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Hedge funds | Fair Value Based on NAV as Practical Expedient | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	1,121,904	852,584
Recurring | Fixed income funds | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	481,039	403,858
Recurring | Fixed income funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Fixed income funds | Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	398,143	290,864
Recurring | Fixed income funds | Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Fixed income funds | Fair Value Based on NAV as Practical Expedient | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	82,896	112,994
Recurring | Equity funds | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	410,149	333,681
Recurring | Equity funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Equity funds | Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	111,040	100,440
Recurring | Equity funds | Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Equity funds | Fair Value Based on NAV as Practical Expedient | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	299,109	233,241
Recurring | CLO equities | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	87,555	39,052
Recurring | CLO equities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | CLO equities | Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | CLO equities | Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	87,555	39,052
Recurring | CLO equities | Fair Value Based on NAV as Practical Expedient | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | CLO equity funds | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	87,509	37,260
Recurring | CLO equity funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | CLO equity funds | Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | CLO equity funds | Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | CLO equity funds | Fair Value Based on NAV as Practical Expedient | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	87,509	37,260
Recurring | Other | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	6,379	9,313
Recurring | Other | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0	0
Recurring | Other | Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	34	578
Recurring | Other | Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	314	315
Recurring | Other | Fair Value Based on NAV as Practical Expedient | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	$ 6,031	8,420
Recurring | Private credit funds | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		33,381
Recurring | Private credit funds | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		0
Recurring | Private credit funds | Significant Other Observable Inputs (Level 2) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		0
Recurring | Private credit funds | Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		0
Recurring | Private credit funds | Fair Value Based on NAV as Practical Expedient | Other investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		$ 33,381