Variable Interest Entities and Noncontrolling Interests - Other variable interest entity disclosures (Details) - USD ($) $ in Thousands		Mar. 31, 2022	Dec. 31, 2021
Variable Interest Entity [Line Items]
Total VIE Assets		$ 45,677,941	$ 45,100,945
Maximum Exposure to Loss, Total		3,472,261	3,248,206
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Total VIE Assets		4,273,436	4,336,596
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(3,696)	(4,434)
Maximum Exposure to Loss - Off-Balance Sheet		40,775	42,202
Maximum Exposure to Loss, Total		37,079	37,768
Remaining Coverage, Amount		331,022
Variable Interest Entity, Not Primary Beneficiary | 2017-1 Ltd. (Oct-17)
Variable Interest Entity [Line Items]
Total VIE Assets		81,415	108,368
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(90)	(159)
Maximum Exposure to Loss - Off-Balance Sheet		380	424
Maximum Exposure to Loss, Total		290	265
Variable Interest Entity, Not Primary Beneficiary | 2018-1 Ltd. (Apr-18)
Variable Interest Entity [Line Items]
Total VIE Assets		147,647	181,136
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(384)	(528)
Maximum Exposure to Loss - Off-Balance Sheet		1,176	1,268
Maximum Exposure to Loss, Total		792	740
Variable Interest Entity, Not Primary Beneficiary | 2018-3 Ltd. (Oct-18)
Variable Interest Entity [Line Items]
Total VIE Assets		283,088	302,563
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(707)	(1,018)
Maximum Exposure to Loss - Off-Balance Sheet		1,953	2,496
Maximum Exposure to Loss, Total		1,246	1,478
Variable Interest Entity, Not Primary Beneficiary | 2019-1 Ltd. (Mar-19)
Variable Interest Entity [Line Items]
Total VIE Assets		157,397	181,324
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(135)	(380)
Maximum Exposure to Loss - Off-Balance Sheet		1,407	5,807
Maximum Exposure to Loss, Total		1,272	5,427
Variable Interest Entity, Not Primary Beneficiary | 2019-2 Ltd. (Apr-19)
Variable Interest Entity [Line Items]
Total VIE Assets		398,316	398,316
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(379)	(515)
Maximum Exposure to Loss - Off-Balance Sheet		5,906	3,998
Maximum Exposure to Loss, Total		5,527	3,483
Variable Interest Entity, Not Primary Beneficiary | 2019-3 Ltd. (Jul-19)
Variable Interest Entity [Line Items]
Total VIE Assets		347,583	409,859
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(298)	(584)
Maximum Exposure to Loss - Off-Balance Sheet		2,783	3,190
Maximum Exposure to Loss, Total		2,485	2,606
Variable Interest Entity, Not Primary Beneficiary | 2019-4 Ltd. (Oct-19)
Variable Interest Entity [Line Items]
Total VIE Assets		352,232	411,954
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(251)	(462)
Maximum Exposure to Loss - Off-Balance Sheet		4,728	4,759
Maximum Exposure to Loss, Total		4,477	4,297
Variable Interest Entity, Not Primary Beneficiary | Bellemeade 2020-2 Ltd (Sep-20)
Variable Interest Entity [Line Items]
Total VIE Assets		185,380	217,766
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(36)	(177)
Maximum Exposure to Loss - Off-Balance Sheet		1,800	1,984
Maximum Exposure to Loss, Total		1,764	1,807
Remaining Coverage, Amount	[1]	784
Variable Interest Entity, Not Primary Beneficiary | Bellemeade 2020-3 Ltd
Variable Interest Entity [Line Items]
Total VIE Assets		324,869	348,818
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		47	(128)
Maximum Exposure to Loss - Off-Balance Sheet		5,088	5,793
Maximum Exposure to Loss, Total		5,135	5,665
Remaining Coverage, Amount	[1]	12,175
Variable Interest Entity, Not Primary Beneficiary | Bellemeade 2020-4 Ltd
Variable Interest Entity [Line Items]
Total VIE Assets		145,747	176,826
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		56	(50)
Maximum Exposure to Loss - Off-Balance Sheet		1,528	1,630
Maximum Exposure to Loss, Total		1,584	1,580
Remaining Coverage, Amount	[1]	7,249
Variable Interest Entity, Not Primary Beneficiary | Bellemeade 2021-1 Ltd
Variable Interest Entity [Line Items]
Total VIE Assets		543,457	568,986
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(600)	(303)
Maximum Exposure to Loss - Off-Balance Sheet		3,596	3,283
Maximum Exposure to Loss, Total		2,996	2,980
Remaining Coverage, Amount	[1]	54,795
Variable Interest Entity, Not Primary Beneficiary | Bellemeade 2021-2 Ltd. (Jun-21)
Variable Interest Entity [Line Items]
Total VIE Assets		514,932	522,807
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(111)	281
Maximum Exposure to Loss - Off-Balance Sheet		4,392	4,124
Maximum Exposure to Loss, Total		4,281	4,405
Remaining Coverage, Amount	[1]	91,241
Variable Interest Entity, Not Primary Beneficiary | Bellemeade 2021-3 Ltd
Variable Interest Entity [Line Items]
Total VIE Assets		507,873	507,873
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(779)	(411)
Maximum Exposure to Loss - Off-Balance Sheet		3,574	3,446
Maximum Exposure to Loss, Total		2,795	$ 3,035
Remaining Coverage, Amount	[1]	131,518
Variable Interest Entity, Not Primary Beneficiary | Bellemeade 2022-1 Ltd.
Variable Interest Entity [Line Items]
Total VIE Assets		283,500
Maximum Exposure to Loss - On-Balance Sheet (Asset) Liability		(29)
Maximum Exposure to Loss - Off-Balance Sheet		2,464
Maximum Exposure to Loss, Total		2,435
Remaining Coverage, Amount	[1]	$ 33,260

[1] Coverage from a separate panel of reinsurers remaining at March 31, 2022.