Investment Information - Allowance for expected credit losses (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Balance at beginning of period		$ 2,883
Balance at end of period		41,355	$ 2,883
Fixed maturities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Balance at beginning of period		2,883	2,397
Additions for current-period provision for expected credit losses		55,636	3,542
Additions (reductions) for previously recognized expected credit losses		(11,789)	(1,258)
Reductions due to disposals (2)		(5,375)	(1,798)	[1]
Balance at end of period		41,355	2,883
Fixed maturities | Structured securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Balance at beginning of period	[2]	802	1,490
Additions for current-period provision for expected credit losses	[2]	14,184	602
Additions (reductions) for previously recognized expected credit losses	[2]	(3,184)	(847)
Reductions due to disposals (2)	[2]	(2,379)	(443)	[1]
Balance at end of period	[2]	9,423	802
Fixed maturities | Municipal bonds
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Balance at beginning of period		2	11
Additions for current-period provision for expected credit losses		359	0
Additions (reductions) for previously recognized expected credit losses		(261)	(9)
Reductions due to disposals (2)		0	0	[1]
Balance at end of period		100	2
Fixed maturities | Non-US government securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Balance at beginning of period		82	0
Additions for current-period provision for expected credit losses		1,616	82
Additions (reductions) for previously recognized expected credit losses		275	0
Reductions due to disposals (2)		(91)	0	[1]
Balance at end of period		1,882	82
Fixed maturities | Corporate bonds
Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items]
Balance at beginning of period		1,997	896
Additions for current-period provision for expected credit losses		39,477	2,858
Additions (reductions) for previously recognized expected credit losses		(8,619)	(402)
Reductions due to disposals (2)		(2,905)	(1,355)	[1]
Balance at end of period		$ 29,950	$ 1,997

[1] Reduction for the 2021 periods primarily related to the Company’s deconsolidation of Somers.

[2] Includes asset backed securities, mortgage backed securities and commercial mortgage backed