Investments (Credit Quality Indicators) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Recording investment gross of allowance for credit losses	$ 4,401,675	$ 2,838,511
Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	476,114	518,611
One Year Prior	1,234,975	311,413
Two Year Prior	356,783	544,189
Three Year Prior	506,703	260,828
Four Year Prior	265,735	309,083
Prior	1,319,305	722,051
Recording investment gross of allowance for credit losses	4,159,615	2,666,175
Commercial mortgage loans | ≥ 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	476,114	501,456
One Year Prior	1,228,561	195,164
Two Year Prior	244,892	481,289
Three Year Prior	446,081	253,938
Four Year Prior	249,203	289,443
Prior	1,185,016	638,092
Recording investment gross of allowance for credit losses	3,829,867	2,359,382
Commercial mortgage loans | 1.0X to 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	17,155
One Year Prior	6,414	109,862
Two Year Prior	84,070	39,577
Three Year Prior	26,681	6,890
Four Year Prior	16,532	7,100
Prior	48,303	39,213
Recording investment gross of allowance for credit losses	182,000	219,797
Commercial mortgage loans | Less than 1.0X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	0
One Year Prior	0	6,387
Two Year Prior	27,821	23,323
Three Year Prior	33,941	0
Four Year Prior	0	12,540
Prior	85,986	44,746
Recording investment gross of allowance for credit losses	147,748	86,996
Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	37,995	98,579
One Year Prior	132,328	26,581
Two Year Prior	26,783	16,226
Three Year Prior	16,089	6,463
Four Year Prior	6,332	8,372
Prior	22,533	16,115
Recording investment gross of allowance for credit losses	242,060	172,336
Agricultural Property Loans | ≥ 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	37,995	98,579
One Year Prior	132,328	26,581
Two Year Prior	26,783	16,226
Three Year Prior	16,089	6,463
Four Year Prior	6,332	8,372
Prior	22,533	15,300
Recording investment gross of allowance for credit losses	242,060	171,521
Agricultural Property Loans | 1.0X to 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	0
One Year Prior	0	0
Two Year Prior	0	0
Three Year Prior	0	0
Four Year Prior	0	0
Prior	0	0
Recording investment gross of allowance for credit losses	0	0
Agricultural Property Loans | Less than 1.0X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	0
One Year Prior	0	0
Two Year Prior	0	0
Three Year Prior	0	0
Four Year Prior	0	0
Prior	0	815
Recording investment gross of allowance for credit losses	0	815
0%-59.99% | Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	90,906	47,161
One Year Prior	226,541	0
Two Year Prior	36,873	179,682
Three Year Prior	155,892	76,656
Four Year Prior	102,585	126,934
Prior	897,176	553,022
Recording investment gross of allowance for credit losses	1,509,973	983,455
0%-59.99% | Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	37,995	98,579
One Year Prior	132,328	26,581
Two Year Prior	26,783	16,226
Three Year Prior	16,089	6,463
Four Year Prior	6,332	8,372
Prior	22,533	16,115
Recording investment gross of allowance for credit losses	242,060	172,336
60%-69.99% | Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	219,322	307,999
One Year Prior	596,059	225,330
Two Year Prior	215,695	289,322
Three Year Prior	273,141	170,444
Four Year Prior	160,422	126,159
Prior	305,514	116,654
Recording investment gross of allowance for credit losses	1,770,153	1,235,908
60%-69.99% | Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	0
One Year Prior	0	0
Two Year Prior	0	0
Three Year Prior	0	0
Four Year Prior	0	0
Prior	0	0
Recording investment gross of allowance for credit losses	0	0
70%-79.99% | Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	165,886	163,451
One Year Prior	412,375	86,083
Two Year Prior	104,215	75,185
Three Year Prior	77,670	13,728
Four Year Prior	2,728	55,032
Prior	97,763	51,203
Recording investment gross of allowance for credit losses	860,637	444,682
70%-79.99% | Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	0
One Year Prior	0	0
Two Year Prior	0	0
Three Year Prior	0	0
Four Year Prior	0	0
Prior	0	0
Recording investment gross of allowance for credit losses	0	0
80% or greater | Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	0
One Year Prior	0	0
Two Year Prior	0	0
Three Year Prior	0	0
Four Year Prior	0	958
Prior	18,852	1,172
Recording investment gross of allowance for credit losses	18,852	2,130
80% or greater | Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	0
One Year Prior	0	0
Two Year Prior	0	0
Three Year Prior	0	0
Four Year Prior	0	0
Prior	0	0
Recording investment gross of allowance for credit losses	$ 0	$ 0