Fair Value Measurements - Change in Level 3 Assets (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 4	$ 5
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)	0	0
Included in other comprehensive income	0	0
Purchases	0	1
Sales	0	0
Transfers into Level 3	11	0
Transfers out of Level 3	0	0
Ending balance	15	6
Corporate Fixed Maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	2	3
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)	0	0
Included in other comprehensive income	0	0
Purchases	0	0
Sales	0	0
Transfers into Level 3	6	0
Transfers out of Level 3	0	0
Ending balance	8	3
Commercial Mortgage Backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	0
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)	0	0
Included in other comprehensive income	0	0
Purchases	0	0
Sales	0	0
Transfers into Level 3	5	0
Transfers out of Level 3	0	0
Ending balance	5	0
States, Municipalities And Political Subdivisions Fixed Maturities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	0	1
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)	0	0
Included in other comprehensive income	0	0
Purchases	0	0
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	0	1
Preferred Equities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	2	1
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)	0	0
Included in other comprehensive income	0	0
Purchases	0	1
Sales	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending balance	$ 2	$ 2