Investment Information - Allowance for expected credit losses (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2021		Sep. 30, 2020	Sep. 30, 2021		Sep. 30, 2020
Allowance for expected credit losses
Balance at beginning of period					$ 2,397
Balance at end of period		$ 2,111			$ 2,111
Accounting Standards Update					Accounting Standards Update 2016-13 [Member]
Available for sale
Allowance for expected credit losses
Balance at beginning of period		2,124		$ 5,869	$ 2,397		$ 0
Cumulative effect of accounting change	[1]						634
Additions for current-period provision for expected credit losses		48		229	2,710		10,578
Additions (reductions) for previously recognized expected credit losses		405		(1,560)	(1,317)		(5,815)
Reductions due to disposals (3)		(466)	[2]	(605)	(1,679)	[2]	(1,464)
Balance at end of period		2,111		3,933	2,111		3,933
Available for sale | Structured securities
Allowance for expected credit losses
Balance at beginning of period	[3]	759		1,726	1,490		0
Cumulative effect of accounting change	[1],[3]						517
Additions for current-period provision for expected credit losses	[3]	48		27	282		2,868
Additions (reductions) for previously recognized expected credit losses	[3]	14		403	(751)		(903)
Reductions due to disposals (3)	[3]	(234)	[2]	(28)	(434)	[2]	(354)
Balance at end of period		587		2,128	587		2,128
Available for sale | Municipal bonds
Allowance for expected credit losses
Balance at beginning of period		6		28	11		0
Cumulative effect of accounting change	[1]						0
Additions for current-period provision for expected credit losses		0		0	0		67
Additions (reductions) for previously recognized expected credit losses		(4)		33	(9)		8
Reductions due to disposals (3)		0	[2]	0	0	[2]	(14)
Balance at end of period		2		61	2		61
Available for sale | Corporate bonds
Allowance for expected credit losses
Balance at beginning of period		1,359		4,115	896		0
Cumulative effect of accounting change	[1]						117
Additions for current-period provision for expected credit losses		0		202	2,428		7,643
Additions (reductions) for previously recognized expected credit losses		395		(1,996)	(557)		(4,920)
Reductions due to disposals (3)		(232)	[2]	(577)	(1,245)	[2]	(1,096)
Balance at end of period		$ 1,522		$ 1,744	$ 1,522		$ 1,744

[1] Adoption of ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326)”

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

[3] Includes asset backed securities, mortgage backed securities and commercial mortgage backed securities.