Investments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended											12 Months Ended
	Dec. 31, 2011 Investment	Dec. 31, 2010 Investment	Dec. 31, 2009 Investment	Dec. 31, 2011 Debt Securities Investment	Dec. 31, 2010 Debt Securities Investment	Dec. 31, 2009 Debt Securities Investment	Dec. 31, 2011 Equity Securities Investment	Dec. 31, 2010 Equity Securities Investment	Dec. 31, 2009 Equity Securities Investment	Dec. 31, 2011 Equity Securities Maximum	Dec. 31, 2011 Procter And Gamble Company And Exxon Mobile Corporation	Dec. 31, 2009 Retained Earnings	Dec. 31, 2009 Accumulated Other Comprehensive Income (Loss)	Dec. 31, 2009 Below 70 percent of cost Debt Securities Investment	Dec. 31, 2011 Two Primary Contributors Investment	Dec. 31, 2011 On Deposit with Various States
Gain (Loss) on Investments [Line Items]
Number of securities															2
Unrealized investment gains due to a net gain position	$ 1,542	$ 1,299		$ 713	$ 515		$ 829	$ 784			$ 213
Fixed maturities, fair value of hybrid securities	59
Other-than-temporary impairment charges	0	0
Investments, deposit with various states	86
Investments in fair value, deposit with various states																93
Impaired securities	12	15	50
Number of securities total unrealized loss in an unrealized loss position for 12 months or more				20	17	121	2	3	10					8
Investments securities total unrealized loss in an unrealized loss position for 12 months or more	5	5		5	4	25		1	26	1				2
Cumulative effect of change in accounting for other-than-temporary impairments as of April 1, 2009, net of tax												$ 106	$ (106)