Segment Information (Total Revenues of Reportable Segments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 3,227,531	$ 3,145,310	$ 9,597,146	$ 9,283,326
Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,838,638	1,785,553	5,335,779	5,367,576
CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	308,130	293,525	947,514	850,883
EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	448,723	438,013	1,403,861	1,255,413
Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	594,202	578,592	1,817,099	1,683,787
Corporate and Other [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	37,838	49,627	92,893	125,667
Life Insurance Product Line [Member] | Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,547,790	1,521,383	4,601,631	4,532,584
Life Insurance Product Line [Member] | CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	295,962	281,095	910,480	814,643
Life Insurance Product Line [Member] | EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	357,059	360,972	1,123,379	1,024,978
Life Insurance Product Line [Member] | Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	578,035	561,660	1,763,094	1,628,419
Nontraditional Long-Duration Contracts [Member] | Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	290,848	264,170	734,148	834,992
Nontraditional Long-Duration Contracts [Member] | CANADA
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	12,168	12,430	37,034	36,240
Nontraditional Long-Duration Contracts [Member] | EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	91,664	77,041	280,482	230,435
Nontraditional Long-Duration Contracts [Member] | Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 16,167	$ 16,932	$ 54,005	$ 55,368