Fair Value - Level 3 Assets (Details) - Level 3 - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Roll forward of level 3 fair value measurements on a recurring basis
Beginning balance	$ 30,546	$ 24,036	$ 26,224	$ 11,645
Included in earnings	(75)	151	(253)	89
Included in other comprehensive income	(165)	499	(535)	120
Purchases	2,224	6,638	11,664	17,410
Sales	(5,248)	(198)	(7,405)	(1,027)
Transfers into Level 3	6,510	41,989	17,033	58,917
Transfers out of Level 3	(11,053)	(2,001)	(23,989)	(16,040)
Ending balance	22,739	71,114	22,739	71,114
Available-for-sale securities
Roll forward of level 3 fair value measurements on a recurring basis
Beginning balance	29,546	23,241	26,224	11,645
Included in earnings	(88)	(43)	(271)	(80)
Included in other comprehensive income	(165)	499	(535)	120
Purchases	2,224	4,622	10,664	14,574
Sales	(5,248)	(198)	(7,405)	(1,027)
Transfers into Level 3	5,417	41,989	14,850	58,917
Transfers out of Level 3	(11,053)	(2,001)	(22,894)	(16,040)
Ending balance	20,633	68,109	20,633	68,109
Corporate debt securities | Available-for-sale securities
Roll forward of level 3 fair value measurements on a recurring basis
Beginning balance	6,078	4,916	5,825	8,324
Included in earnings	7	4	27	9
Included in other comprehensive income	3	157	82	(354)
Purchases	1,995	2,258	4,253	4,759
Sales	(1,213)	(198)	(1,886)	(740)
Transfers into Level 3	1,129	1,644	3,678	9,681
Transfers out of Level 3	(1,802)	(1,751)	(5,782)	(14,649)
Ending balance	6,197	7,030	6,197	7,030
Collateralized debt obligations | Available-for-sale securities
Roll forward of level 3 fair value measurements on a recurring basis
Beginning balance	750	259	0	0
Included in earnings	0	0	0	0
Included in other comprehensive income	0	(9)	0	3
Purchases	0	0	750	247
Sales	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	(750)	(250)	(750)	(250)
Ending balance	0	0	0	0
Commercial mortgage-backed securities | Available-for-sale securities
Roll forward of level 3 fair value measurements on a recurring basis
Beginning balance	17,133	18,066	19,462	3,321
Included in earnings	(90)	(47)	(287)	(89)
Included in other comprehensive income	(143)	351	(590)	471
Purchases	229	2,077	3,073	9,281
Sales	(2,912)	0	(3,878)	(287)
Transfers into Level 3	0	29,786	3,854	38,677
Transfers out of Level 3	(4,523)	0	(11,940)	(1,141)
Ending balance	9,694	50,233	9,694	50,233
Residential mortgage-backed securities | Available-for-sale securities
Roll forward of level 3 fair value measurements on a recurring basis
Beginning balance	3,041	0	937	0
Included in earnings	(5)	0	(11)	0
Included in other comprehensive income	(26)	0	(26)	0
Purchases	0	287	0	287
Sales	(366)	0	(842)	0
Transfers into Level 3	4,288	10,559	7,318	10,559
Transfers out of Level 3	(2,644)	0	(3,088)	0
Ending balance	4,288	10,846	4,288	10,846
Other debt securities | Available-for-sale securities
Roll forward of level 3 fair value measurements on a recurring basis
Beginning balance	2,544		0
Included in earnings	0		0
Included in other comprehensive income	1		(1)
Purchases	0		2,588
Sales	(757)		(799)
Transfers into Level 3	0		0
Transfers out of Level 3	(1,334)		(1,334)
Ending balance	454		454
Nonredeemable preferred stock | Nonredeemable preferred stock
Roll forward of level 3 fair value measurements on a recurring basis
Beginning balance	1,000	795	0	0
Included in earnings	13	194	18	169
Included in other comprehensive income	0	0	0	0
Purchases	0	2,016	1,000	2,836
Sales	0	0	0	0
Transfers into Level 3	1,093	0	2,183	0
Transfers out of Level 3	0	0	(1,095)	0
Ending balance	$ 2,106	$ 3,005	$ 2,106	$ 3,005