Segment Information (Reconciliation of Revenue from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 3,278,518	$ 3,227,531	$ 3,195,908	$ 3,173,707	$ 3,232,443	$ 3,145,310	$ 3,129,276	$ 3,008,740	$ 12,875,664	$ 12,515,769	$ 11,521,511
Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									7,202,978	7,250,549	6,805,414
Canada Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,272,992	1,152,458	1,164,942
EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,844,491	1,673,146	1,535,667
Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									2,471,327	2,284,461	1,834,532
Corporate and Other [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									83,876	155,155	180,956
Life Insurance Product Line [Member] | Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									6,295,733	6,100,171	5,964,968
Life Insurance Product Line [Member] | Canada Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,224,404	1,103,520	1,118,004
Life Insurance Product Line [Member] | EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,494,605	1,362,075	1,195,149
Life Insurance Product Line [Member] | Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									2,416,848	2,210,686	1,771,150
Other Insurance Product Line [Member] | Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									907,245	1,150,378	840,446
Other Insurance Product Line [Member] | Canada Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									48,588	48,938	46,938
Other Insurance Product Line [Member] | EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									349,886	311,071	340,518
Other Insurance Product Line [Member] | Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									$ 54,479	$ 73,775	$ 63,382