Reinsurance (Assumed Life Reinsurance Programs Involving Minimum Benefit Guarantees Under Annuity Contracts - Narrative) (Detail) - USD ($) $ in Millions	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Guaranteed Minimum Death Benefit
Net Amount at Risk by Product and Guarantee [Line Items]
reported liability	$ 83		$ 117
GLB
Net Amount at Risk by Product and Guarantee [Line Items]
reported liability	897		861		$ 550		$ 853
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value			452		204		559
Level 3 | GLB
Net Amount at Risk by Product and Guarantee [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	$ 456	[1]	$ 452	[2]	$ 204	[3]	$ 559

[1] Excluded from the table above is the portion of the GLB derivative liability classified as Future policy benefits. Refer to Note 5 c) for additional information.

[2] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Excluded from the table above is the portion of the GLB derivative liability classified as Future policy benefits in the Consolidated balance sheets. The liability for GLB reinsurance was $861 million at December 31, 2018 and $550 million at December 31, 2017, which includes a fair value derivative adjustment of $452 million and $204 million, respectively.

[3] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Excluded from the table above is the portion of the GLB derivative liability classified as Future policy benefits in the Consolidated balance sheets. The liability for GLB reinsurance was $550 million at December 31, 2017 and $853 million at December 31, 2016, which includes a fair value derivative adjustment of $204 million and $559 million, respectively.