Segment Information (Total Assets of Reportable Segments) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 66,692,481	$ 64,535,245
Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	39,128,756	39,106,169
CANADA
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,637,207	4,354,792
EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	8,766,335	8,380,703
Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	7,574,054	6,861,723
Corporate and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	7,586,129	5,831,858
Life Insurance Product Line [Member] | Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	18,820,270	19,235,781
Life Insurance Product Line [Member] | CANADA
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,579,658	4,200,792
Life Insurance Product Line [Member] | EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,797,482	3,643,174
Life Insurance Product Line [Member] | Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	6,043,694	5,680,978
Nontraditional Long-Duration Contracts [Member] | Americas [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	20,308,486	19,870,388
Nontraditional Long-Duration Contracts [Member] | CANADA
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	57,549	154,000
Nontraditional Long-Duration Contracts [Member] | EMEA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	4,968,853	4,737,529
Nontraditional Long-Duration Contracts [Member] | Asia Pacific [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 1,530,360	$ 1,180,745