Investments (Details 4) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012	Dec. 31, 2011
Unrealized gain on:
Pretax	$ 1,356		$ 1,290
Deferred Tax and Amounts Attributable to Noncontrolling Interests	(491)		(467)
Net	865	[1]	823	[1]	705	578
Fixed maturities [Member]
Unrealized gain on:
Pretax	2,020		2,035
Deferred Tax and Amounts Attributable to Noncontrolling Interests	(721)		(726)
Net	1,299		1,309
Equity securities [Member]
Unrealized gain on:
Pretax	228		161
Deferred Tax and Amounts Attributable to Noncontrolling Interests	(82)		(57)
Net	146		104
Deferred policy acquisition costs [Member]
Unrealized gain on:
Pretax	(691)		(710)
Deferred Tax and Amounts Attributable to Noncontrolling Interests	242		247
Net	(449)		(463)
Annuity benefits and other liabilities [Member]
Unrealized gain on:
Pretax	(140)		(136)
Deferred Tax and Amounts Attributable to Noncontrolling Interests	49		48
Net	(91)		(88)
Life, accident and health reserves [Member]
Unrealized gain on:
Pretax	(115)		(117)
Deferred Tax and Amounts Attributable to Noncontrolling Interests	40		41
Net	(75)		(76)
Other Liabilities [Member]
Unrealized gain on:
Pretax	54		57
Deferred Tax and Amounts Attributable to Noncontrolling Interests	(19)		(20)
Net	$ 35		$ 37

[1] Includes net unrealized gains of $45 million at March 31, 2013 compared to $33 million at December 31, 2012 related to securities for which only the credit portion of an other-than-temporary impairment has been recorded in earnings.