Investments (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Rollforward of the net unrealized securities gains (losses) on Available-for-Sale securities included in accumulated other comprehensive income
Net unrealized securities gains arising during the period	$ 161	$ 89	$ 181
Net unrealized securities gains arising during the period	451	364	516
Net realized gains and losses on Available-for-Sale securities
Gross realized investment gains	16	48	51
Gross realized investment losses	(1)	(20)	(4)
Other-than-temporary impairments	(17)	(24)	(28)
Total	(2)	4	19
Net Unrealized Securities Gains
Rollforward of the net unrealized securities gains (losses) on Available-for-Sale securities included in accumulated other comprehensive income
Balance at the beginning of the period	1,471	1,215	638
Cumulative effect of accounting change			62
Net unrealized securities gains arising during the period	694	560	794
Reclassification of net securities gains included in net income	2	(5)	(20)
Impact on DAC, DSIC, benefit reserves and reinsurance recoverables	(237)	(299)	(259)
Balance at the end of the period	1,930	1,471	1,215
Deferred Income Tax
Rollforward of the net unrealized securities gains (losses) on Available-for-Sale securities included in accumulated other comprehensive income
Balance at the beginning of the period	(514)	(425)	(222)
Cumulative effect of accounting change			(22)
Net unrealized securities gains arising during the period	(243)	(196)	(278)
Reclassification of net securities gains included in net income	(1)	2	7
Impact on DAC, DSIC, benefit reserves and reinsurance recoverables	83	105	90
Balance at the end of the period	(675)	(514)	(425)
Accumulated Other Comprehensive Loss Related to Net Unrealized Securities Gains
Rollforward of the net unrealized securities gains (losses) on Available-for-Sale securities included in accumulated other comprehensive income
Balance at the beginning of the period	957	790	416
Cumulative effect of accounting change			40
Net unrealized securities gains arising during the period	451	364	516
Reclassification of net securities gains included in net income	1	(3)	(13)
Impact on DAC, DSIC, benefit reserves and reinsurance recoverables	(154)	(194)	(169)
Balance at the end of the period	1,255	957	790
Noncredit related impairments on securities and net unrealized securities losses on previously impaired securities, included in Accumulated Other Comprehensive Income	$ (15)	$ (20)	$ (13)