Consolidated Statement of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	$ 5,451,163
Other comprehensive (loss) gain	(364,426)	$ 12,954	$ 122,325
End of period	5,479,798	5,451,163
Net investment gains	154,488	335,858	267,005
Federal and foreign income taxes	(163,028)	(219,433)	(292,953)
Net income before noncontrolling interests	649,066	553,337	603,485
Unrealized investment gains, before tax	(302,737)	(69,425)
Currency translation adjustments, before tax	(112,099)	64,706
Other comprehensive income (loss), before tax	(414,836)	(4,719)
Unrealized investment gains, tax	50,410	17,673
Currency translation adjustments, tax	0	0
Other comprehensive income (loss), tax	50,410	17,673
Unrealized investment gains, net of tax	(252,327)	(51,752)
Change in unrealized translation adjustments	(112,099)	64,706	(124,193)
Unrealized investment (losses) gains
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	375,421	427,154
Cumulative effect adjustment resulting from changes in accounting principles		(214,539)
Restated beginning of period		160,882
Other comprehensive loss before reclassifications	(246,535)	63,567
Amounts reclassified from AOCI	(5,792)	(115,319)
Other comprehensive (loss) gain	(252,327)	(51,752)
Unrealized investment loss related to non-controlling interest	(46)	19
End of period	(91,491)	375,421	427,154
Unrealized investment (losses) gains | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gains	(7,332)	(177,414)
Federal and foreign income taxes	1,540	62,095
Net income before noncontrolling interests	(5,792)	(115,319)
Currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	(306,880)	(371,586)	(247,393)
Cumulative effect adjustment resulting from changes in accounting principles		0
Restated beginning of period		(306,880)
Other comprehensive loss before reclassifications	(112,099)	64,706
Amounts reclassified from AOCI	0	0
Other comprehensive (loss) gain	(112,099)	64,706
Unrealized investment loss related to non-controlling interest	0	0
End of period	(418,979)	(306,880)	(371,586)
Change in unrealized translation adjustments	(112,099)	64,706	(124,193)
Currency translation adjustments | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gains	0	0
Federal and foreign income taxes	0	0
Net income before noncontrolling interests	0	0
Accumulated other comprehensive (loss) income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning of period	68,541	55,568
Cumulative effect adjustment resulting from changes in accounting principles		(214,539)
Restated beginning of period		(145,998)
Other comprehensive loss before reclassifications	(358,634)	128,273
Amounts reclassified from AOCI	(5,792)	(115,319)
Other comprehensive (loss) gain	(364,426)	12,954
Unrealized investment loss related to non-controlling interest	(46)	19
End of period	(510,470)	68,541	$ 55,568
Accumulated other comprehensive (loss) income | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gains	(7,332)	(177,414)
Federal and foreign income taxes	1,540	62,095
Net income before noncontrolling interests	$ (5,792)	$ (115,319)