Segment Information (Total Assets of Reportable Segments) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 59,766,497	$ 60,514,818
Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	35,081,538	34,562,629
CANADA
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,344,925	4,287,824
EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	8,164,458	8,374,488
Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,315,917	6,114,027
Corporate and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	5,859,659	7,175,850
Life Insurance Product Line [Member] | Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	19,038,145	18,603,423
Life Insurance Product Line [Member] | CANADA
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,203,344	4,161,452
Life Insurance Product Line [Member] | EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,335,264	3,099,495
Life Insurance Product Line [Member] | Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	5,159,546	4,915,442
Nontraditional Long-Duration Contracts [Member] | Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	16,043,393	15,959,206
Nontraditional Long-Duration Contracts [Member] | CANADA
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	141,581	126,372
Nontraditional Long-Duration Contracts [Member] | EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,829,194	5,274,993
Nontraditional Long-Duration Contracts [Member] | Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 1,156,371	$ 1,198,585