Employee Benefits - Fair Values of Pension Plan Assets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 2,717	$ 2,305
Short Term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	37	33
Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	916	814
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,718	1,404
Mortgage Backed Securities [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	217	174
U.S. Government and Government Agency and Authority Obligations [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	224	239
Corporate Bonds [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	371	321
Foreign Government and Government Agency Obligations [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	104	80
Other Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 46	$ 54