Investments (Credit Quality Indicators) (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Recording investment gross of allowance for credit losses	$ 6,759,958	$ 6,160,410
Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	759,462	1,142,205
One Year Prior	1,155,379	782,796
Two Year Prior	772,251	1,261,597
Three Year Prior	1,267,011	363,599
Four Year Prior	345,525	528,288
Prior	1,881,156	1,514,519
Revolving Loans	0
Recording investment gross of allowance for credit losses	6,180,784	5,593,004
Commercial mortgage loans | ≥ 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	713,612	1,038,315
One Year Prior	1,039,629	779,282
Two Year Prior	768,777	1,261,597
Three Year Prior	1,267,011	292,561
Four Year Prior	275,080	497,407
Prior	1,755,968	1,402,831
Revolving Loans	0
Recording investment gross of allowance for credit losses	5,820,077	5,271,993
Commercial mortgage loans | 1.0X to 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	45,850	103,890
One Year Prior	115,750	3,514
Two Year Prior	3,474	0
Three Year Prior	0	0
Four Year Prior	0	15,632
Prior	49,352	40,521
Revolving Loans	0
Recording investment gross of allowance for credit losses	214,426	163,557
Commercial mortgage 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	71,038
Four Year Prior	70,445	15,249
Prior	75,836	71,167
Revolving Loans	0
Recording investment gross of allowance for credit losses	146,281	157,454
Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	19,587	126,949
One Year Prior	109,185	235,585
Two Year Prior	213,289	132,042
Three Year Prior	131,887	25,875
Four Year Prior	25,510	15,824
Prior	43,900	25,771
Revolving Loans	28,604
Recording investment gross of allowance for credit losses	571,962	562,046
Agricultural Property Loans | ≥ 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	18,587	126,949
One Year Prior	95,419	233,585
Two Year Prior	211,289	130,353
Three Year Prior	130,184	24,063
Four Year Prior	23,775	15,824
Prior	43,900	25,771
Revolving Loans	28,604
Recording investment gross of allowance for credit losses	551,758	556,545
Agricultural Property Loans | 1.0X to 1.2X
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	1,000	0
One Year Prior	13,766	2,000
Two Year Prior	2,000	0
Three Year Prior	0	1,812
Four Year Prior	1,735	0
Prior	0	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	18,501	3,812
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	1,689
Three Year Prior	1,703	0
Four Year Prior	0	0
Prior	0	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	1,703	1,689
0%-59.99% | Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	89,035	249,037
One Year Prior	254,068	245,914
Two Year Prior	230,308	482,718
Three Year Prior	480,391	109,249
Four Year Prior	94,393	265,053
Prior	1,197,399	1,068,763
Revolving Loans	0
Recording investment gross of allowance for credit losses	2,345,594	2,420,734
0%-59.99% | Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	19,587	73,774
One Year Prior	89,733	179,375
Two Year Prior	168,400	132,042
Three Year Prior	131,887	25,875
Four Year Prior	23,775	15,824
Prior	43,900	25,771
Revolving Loans	13,789
Recording investment gross of allowance for credit losses	491,071	452,661
60%-69.99% | Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	541,378	675,153
One Year Prior	690,428	355,984
Two Year Prior	362,596	449,878
Three Year Prior	445,103	172,721
Four Year Prior	170,063	225,803
Prior	405,172	206,237
Revolving Loans	0
Recording investment gross of allowance for credit losses	2,614,740	2,085,776
60%-69.99% | Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	47,489
One Year Prior	19,452	56,210
Two Year Prior	37,889	0
Three Year Prior	0	0
Four Year Prior	0	0
Prior	0	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	57,341	103,699
70%-79.99% | Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	126,919	218,015
One Year Prior	210,883	133,343
Two Year Prior	121,583	255,299
Three Year Prior	257,377	77,812
Four Year Prior	77,219	20,924
Prior	57,912	86,806
Revolving Loans	0
Recording investment gross of allowance for credit losses	851,893	792,199
70%-79.99% | Agricultural Property Loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	0	5,686
One Year Prior	0	0
Two Year Prior	7,000	0
Three Year Prior	0	0
Four Year Prior	0	0
Prior	0	0
Revolving Loans	14,815
Recording investment gross of allowance for credit losses	21,815	5,686
80% or greater | Commercial mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current Year	2,130	0
One Year Prior	0	47,555
Two Year Prior	57,764	73,702
Three Year Prior	84,140	3,817
Four Year Prior	3,850	16,508
Prior	220,673	152,713
Revolving Loans	0
Recording investment gross of allowance for credit losses	368,557	294,295
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	1,735	0
Prior	0	0
Revolving Loans	0
Recording investment gross of allowance for credit losses	$ 1,735	$ 0