Fair Value Measurements (Schedule Of Significant Unobservable Inputs Used In Level 3 Liability Valuations) (Detail) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2017		Mar. 31, 2017	[2]	Dec. 31, 2016		Jun. 30, 2016	[2],[3]	Mar. 31, 2016	[3]	Dec. 31, 2015	[2],[3]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurements, Valuation Techniques	[1]	Actuarial model
Minimum [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate	[1]	3.00%
Significant Unobservable Inputs Annuitization Rate	[1]	0.00%
Maximum [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-Duration Contracts, Assumptions by Product and Guarantee, Lapse Rate	[1]	34.00%
Significant Unobservable Inputs Annuitization Rate	[1]	78.00%
Guaranteed Minimum Income Benefit [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value		$ 357	[2]	$ 466		$ 559	[2]	$ 971		$ 839		$ 609
Guaranteed Minimum Income Benefit [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value		$ 357				559
Guaranteed Minimum Income Benefit [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value						$ 559

[1] Discussion of the most significant inputs used in the fair value measurement of GLB and the sensitivity of those assumptions is included within Note 4 a) Guaranteed living benefits.

[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 $684 million at June 30, 2017, and $774 million at March 31, 2017, which includes a fair value derivative adjustment of $357 million and $466 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 $1.3 billion at June 30, 2016, and $1.1 billion at March 31, 2016, which includes a fair value derivative adjustment of $971 million and $839 million, respectively. Assets Liabilities Six Months EndedAvailable-for-Sale Debt SecuritiesEquitysecuritiesShort-term investmentsOtherinvestments OtherderivativeinstrumentsGLB(1)June 30, 2017Foreign Corporatesecurities MBS (in millions of U.S. dollars) Balance – beginning of period$74 $681 $45 $41$25$225 $13$559Transfers into Level 3— 57 — ——— —9Transfers out of Level 3— (67) — ——— (9)—Change in Net Unrealized Gains (Losses) included in OCI2 (8) — 1—3 ——Net Realized Gains/Losses1 (1) — ——— (2)(211)Purchases33 221 1 61424 ——Sales(22) (55) (1) (9)—— ——Settlements(3) (81) — —(32)(9) ——Balance – end of period$85 $747 $45 $39$7$243 $2$357Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date$— $— $— $—$—$— $(2)$(211)(1) 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 $684 million at June 30, 2017, and $853 million at December 31, 2016, which includes a fair value derivative adjustment of $357 million and $559 million, respectively. Assets LiabilitiesSix Months EndedAvailable-for-Sale Debt Securities Equitysecurities Short-term investments Otherinvestments Other derivative instruments GLB(1)June 30, 2016Foreign Corporatesecurities MBS (in millions of U.S. dollars) Balance – beginning of period$57 $174 $53 $16 $— $212 $6 $609Transfers into Level 39 18 — — — — — —Transfers out of Level 3(2) — — — — — — —Change in Net Unrealized Gains (Losses) included in OCI9 11 — (1) — — — —Net Realized Gains/Losses(6) (8) — 1 — — 2 362Purchases (2)32 124 1 23 50 14 2 —Sales(8) (30) (5) (2) — — — —Settlements(4) (8) — — — (10) — —Balance – end of period$87 $281 $49 $37 $50 $216 $10 $971Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date$(5) $(7) $— $— $— $— $2 $362(1) 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 $1.3 billion at June 30, 2016, and $888 million at December 31, 2015, which includes a fair value derivative adjustment of $971 million and $609 million, respectively.(2) Includes acquired invested assets as a result of the Chubb Corp acquisition.