Fair Values of Financial Instruments - Carrying Values and Fair Values of Financial Instruments (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short Term Investments	$ 1,845	$ 2,114
Fixed maturities	38,062	37,091
Equity securities	1,969	1,810
Long Term Debt	3,300	3,300
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short Term Investments	1,845	2,114
Fixed maturities	38,062	37,091
Equity securities	1,969	1,810
Long Term Debt	3,300	3,300
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short Term Investments	1,845	2,114
Fixed maturities	38,062	37,091
Equity securities	1,969	1,810
Long Term Debt	$ 3,989	$ 3,806