Segment Information (Total Revenues of Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 3,627,565	$ 3,227,531	$ 10,515,004	$ 9,597,146
Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,992,538	1,838,638	5,673,797	5,335,779
CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	349,055	308,130	1,027,033	947,514
EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	494,910	448,723	1,471,822	1,403,861
Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	731,588	594,202	2,152,263	1,817,099
Corporate and Other [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	59,474	37,838	190,089	92,893
Life Insurance Product Line [Member] | Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,609,866	1,547,790	4,735,208	4,601,631
Life Insurance Product Line [Member] | CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	324,851	295,962	955,326	910,480
Life Insurance Product Line [Member] | EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	378,110	357,059	1,131,615	1,123,379
Life Insurance Product Line [Member] | Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	685,886	578,035	1,992,475	1,763,094
Nontraditional Long-Duration Contracts [Member] | Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	382,672	290,848	938,589	734,148
Nontraditional Long-Duration Contracts [Member] | CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	24,204	12,168	71,707	37,034
Nontraditional Long-Duration Contracts [Member] | EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	116,800	91,664	340,207	280,482
Nontraditional Long-Duration Contracts [Member] | Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 45,702	$ 16,167	$ 159,788	$ 54,005