Consolidated Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	$ 6,118,342
Other comprehensive gain (loss)	170,177	$ 253,068	$ (364,426)
End of period	6,325,797	6,118,342
Net investment gains	103,000	120,703	154,488
Federal and foreign income taxes	(171,817)	(168,935)	(163,028)
Net income	532,985	683,985	649,066
Unrealized investment gains, before tax	164,645	261,970	(302,737)
Currency translation adjustments, before tax	29,927	37,166
Other comprehensive income (loss), before tax	194,572	299,136
Unrealized investment gains, tax	(24,395)	(46,068)
Currency translation adjustments, tax	0	0
Other comprehensive income (loss), tax	(24,395)	(46,068)
Unrealized investment gains, net of tax	140,250	215,902
Change in unrealized translation adjustments	29,927	37,166	(112,099)
Pre-Tax Income (Loss)	704,802	852,920	812,094
Unrealized Investment Gains (Losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	124,514	(91,491)
Other comprehensive income before reclassifications	114,049	224,011
Amounts reclassified from AOCI	26,201	(8,109)
Other comprehensive gain (loss)	140,250	215,902
Unrealized investment loss related to noncontrolling interest	(2)	103
End of period	289,714	124,514	(91,491)
Unrealized Investment Gains (Losses) | Cumulative Effect, Period Of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	24,952
End of period		24,952
Unrealized Investment Gains (Losses) | Cumulative Effect, Period Of Adoption, Adjusted Balance
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	149,466
End of period		149,466
Unrealized Investment Gains (Losses) | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gains		(10,265)
Federal and foreign income taxes	(6,965)	2,156
Net income	26,201	(8,109)
Unrealized investment gains (losses), before tax	33,166
Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	(381,813)	(418,979)	(306,880)
Other comprehensive income before reclassifications	29,927	37,166
Amounts reclassified from AOCI	0	0
Other comprehensive gain (loss)	29,927	37,166
Unrealized investment loss related to noncontrolling interest	0	0
End of period	(351,886)	(381,813)	(418,979)
Change in unrealized translation adjustments	29,927	37,166	(112,099)
Currency Translation Adjustments | Cumulative Effect, Period Of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	0
End of period		0
Currency Translation Adjustments | Cumulative Effect, Period Of Adoption, Adjusted Balance
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	(381,813)
End of period		(381,813)
Currency Translation Adjustments | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gains		0
Federal and foreign income taxes	0	0
Net income	0	0
Pre-Tax Income (Loss)	0
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	(257,299)	(510,470)
Other comprehensive income before reclassifications	143,976	261,177
Amounts reclassified from AOCI	26,201	(8,109)
Other comprehensive gain (loss)	170,177	253,068
Unrealized investment loss related to noncontrolling interest	(2)	103
End of period	(62,172)	(257,299)	$ (510,470)
Accumulated Other Comprehensive Loss | Cumulative Effect, Period Of Adoption, Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	24,952
End of period		24,952
Accumulated Other Comprehensive Loss | Cumulative Effect, Period Of Adoption, Adjusted Balance
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	(232,347)
End of period		(232,347)
Accumulated Other Comprehensive Loss | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gains		(10,265)
Federal and foreign income taxes	(6,965)	2,156
Net income	26,201	$ (8,109)
Pre-Tax Income (Loss)	$ 33,166