Short-Duration Contracts (Reconciliation of Claims Development to Liability) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Discounted Liabilities, Aggregate Discount	$ (128,391)
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	2,019,290
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Aggregate Reconciling Items	25,336,025
Liability for Claims and Claims Adjustment Expense	27,355,315
Canada Segment Reporting Information [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	150,248
EMEA [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	346,916
Corporate And Other Segment Reporting Information [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claim Adjustment Expense, Other Reconciling Item	122,690
Life Insurance Product Line [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	1,527,827
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	17,940
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	(146,331)
Life Insurance Product Line [Member] | Americas [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	796,181	[1]
Life Insurance Product Line [Member] | Asia Pacific [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	$ 731,646	[1]

[1] 2012-2016 Unaudited.