Supplementary Insurance Information (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		$ 3,397,770	$ 3,239,824
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		43,289,926	38,590,883
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		5,642,755	4,992,074
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		10,543,776	9,841,130	$ 9,248,871
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		2,138,525	2,154,651	1,911,886
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		9,744,133	9,020,957	8,358,066
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		423,038	502,866	381,192
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	1,862,673	1,849,131	1,738,307
US Traditional Segment Reporting Information [Member]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		1,824,874	1,818,572
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		11,727,505	11,343,921
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		1,948,335	1,814,018
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		5,533,256	5,356,321	5,249,571
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		729,757	728,073	699,833
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		5,130,795	4,842,412	4,717,850
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		180,407	191,725	177,255
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	698,121	692,600	698,762
US Non-Traditional Segment Reporting Information [Member]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		420,154	405,623
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		19,420,906	15,127,529
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		20,855	17,876
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		27,203	23,683	24,349
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		706,624	778,473	631,097
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		442,071	458,368	333,107
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		108,697	185,280	133,501
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	105,999	105,146	90,458
Canada Traditional Segment Reporting Information [Member]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		192,661	212,345
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		2,929,568	3,041,790
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		182,343	206,655
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		1,024,021	901,976	928,642
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		199,412	189,018	178,927
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		847,828	757,912	707,428
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		13,097	12,426	10,621
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	251,171	212,964	265,250
Canada Non-Traditional Segment Reporting Information [Member]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		0	0
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		25,574	27,908
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		34,471	1,040
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		43,372	38,229	38,701
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		1,334	5,115	2,692
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		36,808	29,639	36,275
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		0	0	0
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	2,204	2,656	2,718
EMEA Traditional Segment Reporting Information [Member]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		239,161	229,150
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		1,110,194	1,075,786
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		977,530	882,744
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		1,423,199	1,301,640	1,140,062
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		66,242	55,511	50,301
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		1,233,458	1,096,211	999,005
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		26,915	20,570	33,795
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	179,113	174,808	132,290
EMEA Non-Traditional Segment Reporting Information [Member]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		0	0
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		4,540,751	4,741,983
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		34,514	38,044
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		195,333	163,720	180,271
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		133,855	123,258	125,282
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		116,492	153,874	178,014
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		0	0	0
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	37,007	33,683	24,497
Asia Pacific Traditional Segment Reporting Information [Member]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		702,439	552,947
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		1,738,199	1,611,633
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		2,436,473	2,017,920
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		2,296,435	2,053,029	1,681,505
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		95,521	91,675	83,049
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		1,885,355	1,635,728	1,345,951
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		92,231	91,477	24,597
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	261,761	334,695	286,674
Asia Pacific Non-Traditional Segment Reporting Information [Member]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		18,481	21,187
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		1,043,375	1,118,012
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		2,365	6,885
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		866	2,419	5,428
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		40,729	34,529	23,648
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		39,726	40,467	37,976
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		1,691	1,388	1,423
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	19,028	18,790	19,920
Corporate And Other Segment Reporting Information [Member]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Deferred Policy Acquisition Cost		0	0
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Liability for Future Policy Benefit, Loss, Claim and Loss Expense		753,854	502,321
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Policy Claim and Benefit Payable		5,869	6,892
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Premium Revenue		91	113	342
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Net Investment Income		165,051	148,999	117,057
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Benefit, Claim, Loss and Settlement Expenses		11,600	6,346	2,460
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Amortization of Deferred Policy Acquisition Cost		0	0	0
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information, Other Operating Expense	[1]	$ 308,269	$ 273,789	$ 217,738

[1] Includes policy acquisition costs and other insurance expenses, excluding amortization of DAC. Also includes other operating expenses, interest expense, and collateral finance and securitization expense.