Income Taxes (Net Deferred Income Tax Assets/(Liabilities)) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Abstract]
Loss reserve	$ 96,840	$ 66,025
Unearned premium reserve	85,028	75,130
Foreign tax credits	46,109	186,706
Lease liability	31,989	33,042
Net unrecognized losses on benefit plans	19,636	19,818
Equity compensation	6,749	7,229
Other tax credits	4,591	2,294
Uncollectible reinsurance reserve	3,142	3,142
Investment impairments	1,121	3,961
Net operating loss	684	19,027
Deferred expenses	622	517
Unrealized foreign currency losses	597	7,958
Other assets	6,559	5,885
Total deferred tax assets	303,667	430,734
Net fair value income	277,525	266,850
Net unrealized investment gains	84,869	38,074
Deferred acquisition costs	79,994	81,931
Right of use asset	28,822	31,510
Partnership investments	26,119	15,039
Bond market discount	2,257	1,466
Benefit plan assets	1,765	2,333
Other liabilities	5,056	3,796
Total deferred tax liabilities	506,407	440,999
Net deferred tax (liabilities)	$ (202,740)	$ (10,265)