Fair Values of Financial Instruments - Fair Values of Pension Plan Assets Categorized Based Upon Lowest Level of Input (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
Fixed Maturities [Member] | U.S. Government and Government Agency and Authority Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	224	239
Fixed Maturities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	371	321
Fixed Maturities [Member] | Foreign Government and Government Agency Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	104	80
Fixed Maturities [Member] | Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	217	174
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,718	1,404
Other Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	46	54
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	594	486
Level 1 [Member] | Short Term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value
Level 1 [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value
Level 1 [Member] | Fixed Maturities [Member] | U.S. Government and Government Agency and Authority Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value
Level 1 [Member] | Fixed Maturities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value
Level 1 [Member] | Fixed Maturities [Member] | Foreign Government and Government Agency Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value
Level 1 [Member] | Fixed Maturities [Member] | Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value
Level 1 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	573	457
Level 1 [Member] | Other Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	21	29
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	2,105	1,801
Level 2 [Member] | Short Term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	37	33
Level 2 [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	909	812
Level 2 [Member] | Fixed Maturities [Member] | U.S. Government and Government Agency and Authority Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	224	238
Level 2 [Member] | Fixed Maturities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	370	321
Level 2 [Member] | Fixed Maturities [Member] | Foreign Government and Government Agency Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	104	79
Level 2 [Member] | Fixed Maturities [Member] | Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	211	174
Level 2 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1,145	947
Level 2 [Member] | Other Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	14	9
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	18	18
Level 3 [Member] | Short Term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value
Level 3 [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	7	2
Level 3 [Member] | Fixed Maturities [Member] | U.S. Government and Government Agency and Authority Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		1
Level 3 [Member] | Fixed Maturities [Member] | Corporate Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	1
Level 3 [Member] | Fixed Maturities [Member] | Foreign Government and Government Agency Obligations [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value		1
Level 3 [Member] | Fixed Maturities [Member] | Mortgage Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	6
Level 3 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value
Level 3 [Member] | Other Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value	$ 11	$ 16